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The Butterflies of the Eastern United States 
AND Canada, with Special Reference to New England. 
3 vols., Imp. 8vo, 2,000 pp. 96 Plates and Maps, plain 
and colored. Half Levant, gilt top, ^75.00. 

Published by Houghton^ Mifflin^ &* C<?., Boston^ Mass. 

Butterflies: Their Structure, Changes, and Life Histories, 
with Special Reference to American Forms. With an 
Appendix of Practical Instructions. i2mo, 332 pp. 201 
Figures. Cloth, {^1.50. 

Published by Henry Holt &> Co., New York, N. Y. 

A Brief Guide to the Commoner Butterflies of 

the Northern United States.** i2mo, 12 + 206 pp. 

Published by Henry Holt <5r» Co., New York, N. Y. 

Fossil Butterflies. 4to, 100 pp. 3 Plates. Paper, ^2.00. 

Published by the A merican Association for the 
Advancement of Scietice, Salenty Mass. 

Historical Sketch of the Genfric Names pro- 
posed for Butterflies : A Contribution to System- 
atic Nomenclature. 8vo, 203 pp. Paper, {pi. 00. 
Soldby the Cambridge Entomological Club, Cambridge, Mass. 


A Students' Manual of the Butterflies of North 
America, north of Mexico. 



t/1 Chapter in Statural History Jor 
the General l(eader 

BY 1 V;- '* 

He hath set the world in their heart, yet so that man 
cannot find out the work that God hath done from the 
beginning even unto the end. — Ecclbsxastbs iii. ii. 



CopyHght, 189S, 
By Samuel H. Scudder. 









Preface 9 

I. General Account of the Milkweed 

Butterfly 11 

11. The Tongue, and How it Works . . 23 

III. The Course of its Life: One Phase 

OF THE "Struggle for Existence" 
AMONG Butterflies 30 

IV. Its Vagrancy : A Lesson in Geograph- 

ical Distribution 40 

V. The Critical Periods of its Life. . 66 
VI. A Favored Race: Mimicry and Pro- 
tective Resemblance 79 

VII. Scent Scales : A Question of Sexual 

Selecfion 96 

VIII. Insect Vision. Does Sight or Smell 

MOST control the ACTION OF BUT- 

IX. The Fore Legs of the Male and the 
Hanging of the Chrysalis : a Les- 
son IN Classification 133 

X. What is its Proper Name? A Brief 
Chapter on Nomenclature as used 
BY Naturalists 148 

8 Contents. 


XI. Some Points not touched upon, aistd 
SOME Things we do not yet suf- 
ficiently know: a Suggestion 
FOR Future Study 157 

Explanation of the Plates iSo 

Index ••••••.. 183 


In the following work I have tried to present 
in untechnical language the story of the life 
of one of our most conspicuous American 
butterflies. At the same time, by introducing 
into the account of its anatomy, development, 
distribution, enemies, and seasonal changes 
some comparisons with the more or less dis- 
similar structure and life of other butterflies, 
and particularly of our native forms, I have 
endeavored to give, in some fashion and in 
brief space, a general account of the lives of 
the whole tribe. By using a single butterfly as 
a special text, one may discourse at pleasure 
of many; and in the limited field which our 
native butterflies cover, this method has a cer- 
tain advantage from its simplicity and direct- 
ness, and I trust may in this instance be of 

There is little in the volume, either in the 
statement of facts or their discussion, which 

10 Preface, 

has not already been published. But as such 
accounts are scattered in many bulky works, 
which only occasionally come under the eye 
of the general reader, for whom this work is 
intended, the presentation of the facts within 
the compass of a single volume may interest 
a larger audience, and perhaps gain for butter- 
flies the serious study of some who had before 
looked at them as merely pretty creatures, — 
types of the frivolous. 

There is, however, one point barely suggested 
before, which is here pretty fully discussed, — 
the question whether the particular butterfly 
chosen as the centre-piece of the work can 
strictly be regarded as a proper denizen of 
regions as far north as New England, where 
it nevertheless occurs abundantly year after 
year. In short, in a volume devoted to our 
native butterflies and meant to inspire an in- 
terest in them, I am attempting to show that 
my principal figure is, after all, but a tropical 

Cambridge, Mass. 



General Account of the Milkweed Butterfly. 

1HERE is probably no other but- 
terfly so well known in every 
part of the United States as 
the Milkweed Butterfly, Anosia pUxippus. 
This is due to its large size, conspicuous 
coloring, wide distribution, and its occa- 
sional remarkable abundance. Of easy, 
quiet flight when undisturbed, often sail- 
ing smoothly with wide-spread wings, yet 
ever ready to do battle with a tempestu- 
ous wind, a reckless adventurer in its 
contrasted livery of orange and black, 
it seems the very beau-ideal of the con- 

1 2 The Life of a Butterfly. 

tented, happy-go-lucky butterfly. It has 
a spread of wing of between four and five 

Examined close at hand we note the 
different form of the fore and hind 
wings, — both broad and ample, but the 
former somewhat falcate, with smoothly 
rounded curves; the latter rather trian- 
gular, but with the outer margin strongly 
arched. A deep orange red forms the 
ground color, but there is a wide margin 
of black on both wings more or less 
dotted with pure white, while the veins 
forming the framework of the wing are 
all traced in black, and across the falcate 
tip of the fore wings is a broad oblique 
black band almost or quite merging into 
the outer black border, and within it a 
couple of rows of more or less sordid 
white spots of a squarish form. The 
body is black, but the thorax is dotted 
with round white spots, and the abdomen 
is narrowly ringed with the same. The 
antennae, nearly as long as the abdomen, 

The Milkweed Butterfly. 13 

are not scaled at all, and have a drooping 
club ; and the black palpi are conspicu- 
ously marked with white, the apical joint 
protruding like a pin tip. Beneath, the 
wings are paler than above, but are very 
similarly marked ; the sides of the body 
are conspicuously dotted with white ; and 
the legs are purplish black with some 
white markings and very long, hardly 
divergent claws. The fore pair, however, 
are very different, being much shortened, 
the tarsal joints reduced to a single one 
(with signs of division in the female) and 
without apical claws. The male is further 
distinguished by possessing at the tip of 
the abdomen an extensile brush of long 
hairs, and on the lower and inner branch 
of the vein, forming the inner margin of 
the discal cell of the hind wings, an apr 
parent thickening of the membrane on one 
side of the vein, really a pouch, which is 
made more conspicuous by its black color. 
The eggs are exceedingly pretty objects, 
3omewhat in the shape of a blunted sugar- 

1 4 The Life of a Butterfly. 

loaf, a little more than a millimetre — or 
less than a twentieth of an inch — high, ' 

amber green in color, the glistening sur- 
face broken up by about twenty-two slight I 
longitudinal ridges, and the interspaces ' 
traversed by straight and fine cross-lines, 
J while the summit of the egg is crowned i 

with a little rosette of cells of extreme 
delicacy. \ 

The caterpillars are striking objects,' — \ 

cylindrical, plump, naked worms, growing 
to the length of nearly two inches, with 
transverse bands of yellow and black. The 
body tapers a little in front, and the head 
is of much smaller diameter than the 
middle of the body, with the face, which 
is yellow, conspicuously marked with two 
parallel black bows ; from the top of the 
second thoracic segment grows a pair of 
long and slender flexible black filaments, 
thrust upward, forward, and a little apart, 
and which have a twitching motion when 
the caterpillar is feeding or alarmed, and 
move alternately forward in marching; a 

The Milkweed Butterfly. 15 

similar, but shorter, more erect and in- 
active pair of black filaments is also 
found on the top of the eighth abdominal 
segment. These filaments are scarcely- 
observable in the first stage of the cater- 
pillar, which is then armed with several 
series of simple, short hairs arising from 
papillae, which are practically lost after- 

The chrysalis is again a very striking 
object, but simply on account of its color- 
ing. It hangs by a slender little peduncle 
of shining black, and is very compact and 
stout, with plump, rounded form and only 
the slightest projections, all of which are 
rounded ; the plumpness is in part due to 
the shortness of the abdomen, the joints 
of which, beyond the third, rapidly shorten 
and contract, leaving at the hinder edge 
of the latter a ridge which encircles the 
body (except the wings) at its stoutest 
part, and is made the more conspicuous 
by bearing little tubercles set in a belt 
of color, shining black in front, nacreous 

1 6 The Life of a Butterfly. 

in the middle, and golden behind, while 
the entire body of the chrysalis is of an 
emerald green, except for a few gilt or 
black dots on other definitely scattered 
tubercles* It is over an inch long, and 
from eleven to twelve millimetres in di- 
ameter at the stoutest part. 

The first spring eggs are usually laid 
near the base of the midrib of either 
surface of the terminal or next to the 
terminal leaves of the young plant of an 
Asclepias, or milkweed, while they are 
still erect or nearly erect. The under 
surface seems to be preferred. Generally 
but one egg will be found on a leaf, and 
not often more than two or three on a 
plant. Later they are also laid upon the 
pedicel of the flower. The egg hatches 
in four days or even slightly less, but is 
sometimes delayed so as not to emerge 
for five days or more. 

The caterpillar feeds upon different 
species of milkweed, Asclepias, although 
"it shows a wonderful dislike," Riley 

The Milkweed Butterfly. ly 

remarks, "to the poke milkweed {A, phy- 
tolaccoides Pursh.). . . . Larvae furnished 
with this plant would wander about their 
breeding-cages day after day, and would 
eventually die rather than touch it." In 
the north it generally appears to confine 
itself to A* comuti Dec, but has been 
found on A, purpurascens Linn, and A. 
incarnata Linn. ; in the south and in 
Missouri, it also feeds on the butterfly 
weed, A. tuberosa Linn., A. amplexicaulis 
Michx., A. tomentosa Ell., and A, curassa- 
vica Linn., and has been taken in Cuba 
by Dr. Gundlach on A. nivea Linn. It 
has been discovered, too, on the dogbane, 
Apocynum, A, androsaemifolium Linn., and 
according to Coquillet will feed also on 

The caterpillar eats voraciously, and 
ordinarily matures rapidly. Sometimes, 
however, it takes three or more weeks to 
attain its gr6wth. When observed toward 
evening it will ordinarily be found quiet, 
apparently resting for the night, planted 

1 8 The Life of a Butterfly. 

on the under surface of the midrib of a 
leaf, half way between the base and apex, 
its head outward. From this it might ap- 
pear that it fed only by day, but caged 
specimens certainly eat at night, and I 
have found it resting early in the morning 
on the top of the leaves on a cloudy day. 
It is almost always found near the top of 
a plant, and when disturbed, so as to be 
knocked off a leaf, the caterpillar coils 
like a galley worm. Dewitz, writing of 
the larva in Venezuela, says it spins a 
thread on being seized, but I cannot 
understand the statement; it spins less 
thread than almost any caterpillar known 
to me. 

When preparing to moult it spins an 
extra amount of silk upon the leaf for a 
good foothold, and rests immovable for 
many hours. The new skin has begun to 
form beneath the old, and while still soft, 
the new head-case is withdrawn from the 
old into the region of the thoracic seg- 
ments, till finally the old skin splits on 

ne Milkweed Butterfly , 19 

the first segment behind the old head- 
case, and the new caterpillar walks out 
from its old skin ; the old head-case falls 
to the ground, and the old skin shrivels 
to almost nothing, and is usually eaten up 
by its former owner. 

I once observed one of these caterpillars 
while moulting ; it had been stationary at 
least twenty-four hours, and now first 
began swaying its body from side to 
side, — ■ falling over so far that the thoracic 
filament of the upper side became per- 
pendicular, and then drawing itself forci- 
bly back to an opposite position. The 
muscular effort caused a considerable 
indentation along the falling side of the 
swaying larva at the point where the 
white band widens, and at which muscles 
are attached. The motion was repeated 
about once in three seconds, and contin- 
ued for nearly three-quarters of an hour ; 
now and then the larva would viokntly 
shake its filaments or strain forward the 
front of the thoracic segments, thus grad- 

20 The Life of a Butterfly. 

ually detaching the old skin from the 

At last, after remaining quiet, as if to 
gather strength for a final effort, it began 
to make violent contortions, especially 
about the thoracic region. These at first 
seemed ineffectual, but suddenly the in- 
tegument parted between the head and 
body, and by the movements of the 
larva, passed backward over the new 
skin, slipping over the whole body at 
once, and leaving a little empty pellicle 
at the hinder extremity. The skin was 
with difficulty removed from the fila- 
ments, especially from one whose tip had 
been bent in the former stage, and which 
only parted after strong exertions; the 
fresh filaments lay limp along the back 
until they were gradually drawn forward, 
the tip clinging to the moist body until 
the last; but they did not regain their 
full elasticity for some time. The re- 
maining process scarcely lasted a minute ; 
the head, however, still remained attached, 

The Milkweed Butterfly. 21 

and was only removed after repeated 
lateral abrasions and violent efforts with 
the front legs. 

After these efforts the insect remained 
quiet, resuming the same attitude, with 
bent head, which it had taken before 
moulting, — awaiting, undoubtedly, the 
hardening of its integuments ; and it was 
nearly two hours before the colors of the 
head became bright and fixed. The larva 
now first devoured all the old pellicle, 
except the head, and then moved off in 
search of daintier diet. 

The chrysalis usually hangs for about 
twelve days, ranging in New England 
generally from nine to fifteen ; but in the 
South, according to Edwards, from five 
to fifteen days ; in one case he reports 
it as reduced to two days ! On the other 
hand, Gundlach says it hangs from eight 
to twelve days in Cuba, and Dewitz gives 
twelve days as the season in Venezuela. 
I have known it to be extended in New 
England to three weeks. 

22 The Life of a Butterfly. 

"At last," says Peale, "the golden spots 
begin to lose their brilliancy and the 
beautiful green disappears; the orange 
wings of the imprisoned butterfly now 
become visible through its temporary sar- 
cophagus, which it bursts open on the fol- 
lowing day, and the liberated insect soon 
takes wing to join its comrades, select 
its mate, and pass the happy hours of a 
brief existence in revelling in the sweets 
of the flowers among which it sprang 
into being." 


The Tongue and How it Works. 

|NE of the most striking things' 
about butterflies, and one which 
never fails to excite the admira- 
tion of the observer, is the way in which 
they feed. Every one has seen them at 
the blossoms of clover, of milkweed, of 
golden-rod, thistle, and phlox; and any 
one who, approaching cautiously, has 
then looked at them from near at hand, 
has seen a wonderful apparatus like a 
watch-spring suddenly uncoil from the 
lower part of the head ; and while the 
tremulous excitement and eagerness of 
its owner is shown by the rapid and 
repeated uncoiling and half coiling again 
of this organ, as well as by the shivering 
palpitation of the wings, the tentative 

24 The Life of a Butterfly. 


thrusts to prob^ the bottom of the gauzy 

dish and the quiet satisfaction of the 

butterfly when this is reached show that 

it is through this slender, flexible thread 

that the sweet fluids of the clover and 

other blossoms are drawn into the body. 

/ This flexible conduit, moreover, is the 

I most characteristic of all the structures 

J peculiar to the order of insects to which 

] butterflies belong, aftd-TfiayT^wett — merit 

C p^rticular-attentioTi. 

Notwithstanding its delicacy, and al- 
though almost entirely concealed when 
coiled, this "tongue" is frequently as 
long as the entire body, and consists of 
two lateral halves united down the 
middle ; each part is composed of an 
\ immense number of short, transverse 
rings, which are convex on the outer 
surface, concave on the inner ; and it is 
by the union of these inner concavities 
that a central tube is formed. The lateral 
rings are also partially hollow, and were 
therefore formerly supposed by some to 

How the Tongue IVorks. 25 

form sucking-tubes, in which case the 
insect might be said to have two mouths, 
for there would be two entrances to the 
throat. This, however, is not the case, 
the interior of each lateral half being 
closed at the end and filled with nerves, 
air-tubes, and muscles. The rings of 
which it is composed are made up of 
a great number of plates, united by the 
more yielding part of the cuticle, allow- 
ing of great freedom of motion. These 
rings, at the points where the convex 
and concave sides meet, are furnished 
with a series of oblique, curving plates 
or hooks, which, when the two lateral 
halves are brought together, interlock in 
the most complete manner, to form a 
perfectly flexible yet impervious tube. 

The external walls of the lateral tubes 
are supplied with curious minute papillae 
of greatly varying shape, size, and abund- 
ance in different groups, but in general, 
more highly organized and abundant in 
the highest butterflies. In our Milkweed 

26 The Life of a Butterfly. 

Butterfly, Burgess tells us, they are seated 
on little circular plates, and are dotted 
all over the outer wall, but especially 
near the tip, and occur also, though in 
much less number, within the central 
canal. In this simple development they 
must be regarded as organs of taste or 
touch, as suggested by Fritz Miiller; but 
in some moths, as in the orange moth, 
they become notched spines, and even act 
as a saw or file, so that the tongue may 
work its way through plant tissues in 
search of juices. The muscles mentioned 
as found in the interior of each lateral 
half of this wonderful structure are ob- 
liquely disposed, serving to coil the whole 
into the watch-spring-like form in which 
it is packed away when not in use. 

Where was this curious and compli- 
cated organ in the caterpillar? From 
what, that is, did it take its rise? One 
will have to look carefully to discover 
it at all ! The principal organs one will 
find in the mouth of the caterpillar are 

How the Tongue Works. 27 

a pair of stout nipping jaws by which 
it bites the leaves on which it feeds ; but 
just behind them, on either side of the 
spinneret, will be seen little hemispherical 
prominences, each with a pair of minute 
appendages, the outer consisting of sev- 
eral joints and closely resembling the 
antennae, the inner and smaller of only 
one ; and it is this wee stiff thing, capable 
only of the slightest motion of withdrawal 
and protrusion on its cushiony base, that 
becomes so enormously developed into 
the complicated watch-spring tongue of 
the butterfly, while the outer appendages 
become in the perfect stage the feath- 
ery-scaled side-pieces which protect the 
tongue when rolled. 

But now that we comprehend the struc- 
ture of this wonderful piece of mechanism, 
and can appreciate the change that has 
been wrought in its development from an 
utterly simple, almost microscopic joint, 
do we understand any better its actual 
use in extracting honey from flowers? 

28 The Life of a Butterfly. 

Some have thought that the upward flow 
was due to capillary motion ; others to the 
action of the so-called sucking stomach, 
a sac-like expansion of the alimentary 
canal just in advance of the true stomach ; 
others still that it is forced on by suc- 
cessive undulations and contractions of 
the tube itself. 

The investigations, however, of one of 
our own naturalists (who afterward dis- 
tinguished himself in the construction of 
the swiftest yachts in the world) has 
shown the existence of a minute mus- 
cular sac within the head, furnished with 
a valve at its front extremity, where it 
opens into the base of the tongue. When 
the radiating muscles running from the 
walls of the head to the periphery 
of this sac are contracted, the sac is 
expanded, and into the vacuum thus 
produced the fluids into which the 
tongue is plunged necessarily ascend. 
On the relaxation of these muscles and 
the squeezing of the sac by the other 

How the Tongue Works. 29 

muscles which encircle it, the fluids now 
in it, prevented by the valve from re- 
treating the way they came, are forced 
down the alimentary canal. When, then, 
we see a butterfly busily engaged upon 
a flower, it requires little imagination to 
picture to one's self a little force-pump 
steadily at work within the dear creature's 
diminutive head, transferring the fluid 
nectar from the base of the flower to the 
greedy stomach. 



The Course of its Life: one Phase of the 
** Struggle for Existence'' among Butter^ 

HE course of life of the Milkweed 
Butterfly is a simple one. Win- 
ter is passed in the perfect or 
'* imago " state, but in what sort of places 
is not known; in the extreme south it 
remains on the wing, but that is not the 
case further north, where the cold would 
make it impossible. In the proper range 
of the species (of which we shall have 
somewhat to say later on) the warmth 
of the early spring lures the hibernating 
butterflies from any places of conceal- 
ment they may have had, faded in color 
but not so often ragged in attire. In 
West Virginia, according to Edwards, 
they may be seen on the blossoms of 

The Course of its Life. 3 1 

the wild plum the last of March, and 
on lilacs and other flowering shrubs in 
April. The tender leaves of the milk- 
weed, on which the caterpillar feeds, are 
just appearing above the ground, and on 
these the females hasten to deposit their 
eggs; they are usually laid on the under 
surface of the terminal leaves while these 
are still vertical. They hatch in four or 
five days; later in the season, in the 
south at least, in two or three days. 

Immediately it has escaped from the 
egg, the caterpillar completely devours 
the shell, as if to leave no manifest token 
to the wily and vigilant ichneumon-fly 
that its former inhabitant was near at 
hand, and then attacks the leaf on which 
it was born, eating a slender hole often 
entirely through it, and when it has done 
feeding retires to the concealed side of 
the leaf, — if it be still erect, to the inner, 
that is the upper side ; if extended hori- 
zontally, to the lower surface. As soon 
as appetite returns, — and it is a voracious 

32 The Life of a Butterfly. 

feeder, — it has its food ready at hand. 
So it eats and rests, and rests and eats, at 
night — to judge from a few observations 
I have made — quite as well as by day, 
except that it is more sluggish in cool 
weather, and nights are cooler than the 
day. In a day or two (the time de- 
pending partly upon the weather), the 
caterpillar makes its first moult, but its 
habits remain much the same. Three 
other similar moults follow before the 
caterpillar has attained its growth, which 
may be acquired in eleven days from 
the egg, though it is usually longer than 
that, and in cool weather may be greatly 

}k Then comes the change to chrysalis, 
to seek a good place for which the cater- 
pillar usually leaves the plant (though I 
have found the chrysalis hanging pendant 
from the leaf) and seeks some such stable 
place as the under side of a fence rail 
or a jutting rock from which to suspend. 
Mr. Edwards once found one on the 

The Course of its Life. 33 

under side of the T rail of a railway 
track! Here it hangs for a variable 
period, — two to fourteen days, according 
to the season and temperature, and per- 
haps the exposure; and the butterfly 
again makes its appearance, the cycle of 
changes complete. 

How often this cycle may be repeated 
during the year is doubtful and certainly 
variable, the weather and latitude being 
undoubtedly again important factors; it 
has been a matter of some dispute. Riley, 
making his observations in Missouri, con* 
siders that there are but two broods 
annually in that region. Edwards, in 
West Virginia, believes there may be 
four or five in his district, and one would 
hardly look for more in the one than in 
the other; but Edwards* belief appears 
to be founded upon the fact of finding 
the insect in all its stages at nearly all 
times the summer through, and upon his 
observations of the time required for the 
entire cycle, which is sometimes as short 
as three weeks. 3 

34 ^*^ Life of a Butterfly. 

He leaves out of account entirely the 
possibility that the parent butterfly may 
lay eggs for a considerable length of time, 
because he does not believe this to be 
the case, and it certainly would be very 
difficult to prove it to be or not to be 
the case in a Southern district; but in a 
more Northern region, where the number 
of broods would be likely to be less than 
at the South, it would not be so difficult, 
and from what information I can gain I 
am very strongly inclined to believe that 
there are at the most two broods a year 
north of the latitude, say, of Washington. 

I shall on a future page explain this 
more fully, in considering the distribution 
of this butterfly, of which I believe there 
is but one brood a year in most of New 
England and northward. I should not 
be surprised if it . should turn out that 
there were nowhere in the United States 
more than three broods a year, and it 
may even yet be proved that there are 
but two. 

The Course of its Life. 35 

In any case, this is one of the simplest 
life-histories we have among our native 
butterflies; and the dispute regarding it, 
and the uncertainty that still surrounds it 
and probably will surround it for a long 
time, show how wide a field for observa- 
tion is open to young naturalists. The 
variations on this theme among our but- 
terflies fire endless. The cycle is inva- 
riable; but winter may intervene at any 
stage, usually at an identical stage in any 
given species, though occasionally at two 
different stages. 

Relatively few butterflies, in New Eng- 
land at least, winter as butterflies; such 
are mostly confined to the Angle-wings 
and their allies, of which Euvanessa an- 
tiopay the Mourning-cloak, is the best 
known example. A considerable number 
are dependent for their perpetuity upon 
the power of resistance to cold possessed 
by the egg; and then the egg is never 
laid upon the leaf of the food plant, 
which would fall to the ground in the 

36 The Life of a Butterfly. 

autumn, but upon the twigs of the same 
or upon some stable point near by if the 
plant be an annual. The caterpillar then 
usually hatches in the earliest spring and 
feeds upon the tender leaves before they 
are fairly unfolded. Such is the case with 
some of the delicate Lycaenids, the Hair- 
streaks, Blues, and Coppers; apparently 
it is more common in this subfamily than 
elsewhere, but it is known to occur in a 
number of widely different butterflies, one 
striking case being that of Parnassius, an 
alpine genus. 

What the condition of the embryo may 
be in these instances is not at all known, 
but it is certain that the cases are not 
few in which the caterpillar hibernates 
without tasting a morsel of food besides 
its own egg-shell, much the same as if it 
had wintered fully formed in the egg. 
The doctors tell us we should never go to 
bed hungry, but here are creatures which 
go to their long winter's rest before they 
have tasted any proper food; this is 

The Course of its Life. 37 

tolerably common among the Satyrids or 

Then there are others which hibernate 
as partly grown or fully grown cater- 
pillars; and these with the last — that is, 
such as hibernate in some larval stage 
or other — include a very considerable 
proportion of our Northern butterflies, 
perhaps even a majority of them. Among 
them should be counted, perhaps, such 
butterflies as our Dusky-wings of the gen- 
era Thanaos and Pholisora, which in the 
autumn prepare for the change to chrysa- 
lis by making a sort of cocoon for the 
purpose; these they never leave again 
as caterpillars, but in them remain quite 
unchanged until the early spring, when 
after a short period in chrysalis they are 
among the earliest butterflies of the 
season. Finally, there is the chrysalis,'*^ 
which really seems made to be the nor- 
mal stage for hibernation for Lepidoptera, 
and one which appears to be the nearly 
universal condition among the moths, but 

38 The Life of a Butterfly. 

which is vastly less common among the 
butterflies, aspiring creatures whose lives 
are as variegated as their broad wings. 

With such a variety, all possible variety, 
in the matter of hibernation, wTiat wonder 
that the lives of butterflies are varied? 
Some pass a single cycle in the course 
of the season, ending where they began, 
some two or more; some among the 
Northern insects appear to take two years 
to complete the cycle, wintering succes- 
sively in two different periods of life ; or 
they may take sometimes one and some- 
times two years, as would appear from 
recent observations in Canada; while to 
cap the climax, there are not a few in- 
stances, confined apparently to regions 
where winter is a prime factor in life, 
and probably resulting therefrom, where 
a butterfly may be at the same time 
single and double brooded, the progeny 
of a single batch of eggs giving birth to 
butterflies partly in the course of the 
same season, partly in the season follow- 

The Course of its Life. 39 

ing, the later butterflies flying with the de- 
scendants of the earlier ; that is, with their 
nephews and nieces! This comes about 
in a curious way, by the premature hiber- 
nation from midsummer on of a certain 
portion of the original brood at just that 
particular time of life when their nephews 
and nieces will hibernate. The tendency 
to hibernate at that specific time of life 
is thrown back into midsummer, when 
there are no signs of provocation thereto. 

The study of the influence of winter 
life upon the histories of our butterflies 
unfolds a curious and perplexing chapter. 
We see what an element it has been in 
the development of these creatures, how 
they have always had to contend with 
it, and in what manifold ways they have 
made their struggle for existence. How 
many may have succumbed! 


Its yagrancy: a Lesson in Geographical 


|ARDLY any other of our North 
American insects equals our 
Milkweed Butterfly in interest 
when we consider its distribution. With 
the exception of a few butterflies which 
we possess in common with Europe, and 
which may have had their origin there, 
no other species is so wide-spread- There 
is still some question whether certain 
butterflies found in the American tropics 
are to be regarded as, with this, varieties 
of one species, or as distinct forms ; but 
without discussing a somewhat unproflt- 
able question, we may better assume, 
what is probably the case, that all belong 
to a single species with local variations. 

Its yagrancy. 41 

This granted, we find our butterfly to 
be a distinctly American form, belonging 
properly to the tropics. It is found all 
over the West India Islands, as well as 
on the mainland, and extends beyond the 
tropics much farther in the north than in 
the south, for its southernmost known 
location in South America is the very 
northern border of Patagonia, in latitude 
40°, while in North America it extends 
over almost every part of the United 
States, no part of which lies within the 
tropics, and even over a large part of 
Canada, having actually been reported 
from the southern borders of Hudson Bay, 
and even from the Ath^ascan region in 
the far northwest, nearly twenty degrees 
farther from the tropics than in South 

Belonging as it does to a distinctively 
tropical group of butterflies, it appears 
here quite out of place. The semi-tropical 
character of the southern United States, 
<u)mewhat more marked than in similar 

42 The Life of a Butterfly. 

latitudes in South America, does not 
make its appearance there surprising ; but 
farther north, beyond Philadelphia (which 
would be latitudinally equivalent to its 
farthest in South America), it clearly 
^ appears like an interloper. Precisely here 
comes in the interesting feature in its 
distribution. We are accustomed to think 
of the butterflies we see as born and bred 
in the district where they are seen. It 
is otherwise with birds; we know that 
very many among them come and go 
with great regularity and for great dis- 
tances, though it is only within given 
latitudinal boundaries that they will breed, 
each in its own domain. It has hardly oc- 
curred to entomologists to inquire whether 
this may not sometimes be the case with 
butterflies. The very fact that some birds 
do and some do not move northward and 
southward with the seasons, should sug- 
gest the possibility that this may be the 
case with other flying creatures. 

Particularly should such a suggestion 

Its Vagrancy, 43 

be heeded in those groups where great 
flocks are known to occur and apparent 
migrations take place. There are two 
such groups represented among our but- 
terflies, one of them that to- which our 
Milkweed Butterfly belongs ; and there 
seems to me nearly every reason to be- 
lieve (what every recurring season of 
observation serves only to strengthen) 
that the natural northern limits of our 
butterfly, are not farther north (perhaps 
much farther south) than about latitude 
40° on the Atlantic border, and that the 
eggs, caterpillars, and chrysalids of the 
butterfly found much north of this are in 
all cases the production of immigrants 
from farther south, — no perfect buttetfly 
born at any considerable distance north 
of this assumed limit ever laying an egg 
the same season. 

Indeed, it is probable — such is in my 
belief the vagrant habit of the butterfly — 
that a butterfly successfully hibernating 
farther south may fly to some distance 


44 The Life of a Butterfly. 

still beyond this before depositing all her 
eggs ; and the progeny from these, though 
born so far north, would again lay eggs. 
But by far the greater part of the eggs 
laid beyond the limit — almost the whole 
of them — are laid by butterflies of the 
second generation, born farther south, and 
wandering northward in search of "fresh 
fields and pastures new ; " and their pro- 
geny will not lay eggs the same season. 

This, let it be at once asserted, is a 
theory only, made to explain the observed 
facts, but appearing at present the best 
way of explaining them. Let us state 
some of these. We have already seen 
that in West Virginia the butterflies ap- 
pear as soon as the first shoots of milk- 
weed arise above the ground in April. 
The same is the case at least as far 
north as Newburgh, New York; that is, 
the first butterflies seen are those which 
by their faded colors are believed to have 
hibernated, and they lay their eggs on the 
milkweed when it first comes out of the 

Its yagrancy. 45 

ground. At Newburgh the season is per- 
haps three weeks or a month later than in 
West Virginia, and at least as far north as 
this, it would seem to be perfectly easy for 
the hibernating butterfly to have flown 
from even as far as Florida. It would 
have had to fly no faster than a man walks, 
counting only the da3^ime and deducting 
half of that for bad weather. 

Still farther north, where observations 
have been quite as numerous as south 
of it, a hibernated butterfly of this 
species is an extraordinary rarity, and 
the first butterflies of the season are those 
which appear when the milkweed is al- 
ready a foot or more above the ground, 
synchronous with or slightly later than 
the descendants of the hibernators farther 
south, fresh and bright butterflies, cer- 
tainly born the same season. According 
to my observations in diflerent parts of 
New England, they are long-lived, laying 
but a few eggs at a time, and probably 
not depositing all until several weeks after 

46 The Life of a Butterfly. 

birth. The butterflies are on the wing 
the rest of the season, — first the parents, 
next their children, the parents grad- 
ually dying out 

There is no evidence whatever of a sec- 
ond brood of caterpillars in New England ; 
that is, that these children ever lay eggs 
the same season. In all double-brooded 
butterflies known in New England, the 
Hmits of their broods can be told, some- 
times it is true rather vaguely. Still there 
appears to be more definiteness here than 
farther south, where the summer is longer; 
and from observations made in numerous 
places by scores of individuals, it appears 
quite plain that our Milkweed Butterfly 
passes in New England but once through 
the entire cycle of its changes; and 
though the theory here proposed finds 
no known counterpart elsewhere, it ap- 
pears to be gaining ground among ob- 
servers. Of course it will require many 
further observations to establish it. 

Among butterflies it is only when 

Its Vagrancy. 47 

large numbers are concerned that their 
movements attract attention. Very many 
such observations are on record, but the 
purpose of the movements has rarely 
been even guessed at. With most but- 
terflies which have more than one brood 
in a year, and notably in our Milkweed 
Butterfly, the number of individuals upon 
the wing toward the end of the season 
is far greater than at the beginning, and 
it would therefore be easier to detect 
massive movements in the later than in 
the earlier part of the season. Now, 
nobody has ever observed that the preva- 
lent movement of our butterfly in the 
earlier part of the season was northward, 
as on the theory here upheld should be 
the case, and this is undoubtedly its weak 
point. Nevertheless I look confidently 
to seeing this observed and proved at no 
distant day, particularly by observers in 
New York and Ohio. 

The fact that the butterfly has been 
seen on the shores of Hudson Bay and in 

48 The Life of a Butterfly. 

the Athabascan region, beyond the limits 
of the growth of its proper food plant,* is 
another proof of its northward migration 
in the warm season. But of the return 
movement in the autumn there is plenty 
of evidence. Apparently wherever it 
abounds in any part of the United States, 
certainly from Ontario to Florida and from 
Massachusetts to Iowa and Missouri, the 
butterfly shows a tendency in the autumn 
to swarm in immense numbers, and at 
night to settle down upon trees or shrubs, 
so as to change the whole effect in color. 
I will give one instance of the many that 
have been published. Writing of Brigan- 
tine Beach, New Jersey, in 1885, Dr. John 
Hamilton, of Alleghany, Penn., says: — 

"The multitude of this butterfly that as- 
sembled here the first week in September is 

* Asclepias is not found about Hudson Bay nor 
north of the Saskatchewan, according to the Canadian 
botanists ; and although Apocynum does occur both in 
the valley of the Moose River and in the Athabascan re- 
gion^ it is too exceptional a food plant to be considered- 

Its Vagrancy. 49 

almost past belief. Millions is but feebly 
expressive, — miles of them is no exaggeration. 
On the island is a strip of ground from one 
hundred and fifty to four hundred yards wide, 
and about two and one half miles in length, 
overgrown with Myrica cerifera (bayberry). 
After three o'clock these butterflies, coming 
from all directions, began to settle on the 
bushes, and by evening every available twig 
was occupied. To see such multitudes at rest, 
all suspended from the lower sides of the 
limbs, side by side, as is their well known 
custom, was something well worth seeing. One 
evening I travelled more than half the distance 
of their encampment, and learned that it 
extended the whole length and breadth of the 
bushes. In the morning they gradually sepa- 
rated, and did not appear unusually numerous 
during the day, but in the afternoon they came 
again as described. I found them on the 
second, the day of my arrival, as related above ; 
and this was repeated daily till the sixth, the 
forenoon of which was rather calm and sultry. 
A storm of wind and rain came on about two 
o'clock^ p. m., continuing till midnight. The 


50 The Life of a Butterfly. 

next afternoon few came to camp; the great 
army had disappeared. But how? when? 
where to? During the next few days they 
appeared again in considerable numbers, — 
about as they had been observed in former 
Septembers, — but insignificant when compared 
with those that preceded. The males and 
females were about equal in numbers. Not a 
single stalk of their food plant (Asclepias) 
grows on the island." * 

This gathering of the clans is but the 
first step in the southward movement, 
which also has been observed in numer- 
ous places. One of the earliest accounts 
we owe to Riley, who states that P. B. 
Sibley, of St. Joseph, Missouri, on Sep- 
tember 19, 1868, saw ** millions of them, 
filling the air to a height of three or four 
hundred feet for several hours, flying 
from north to south." 

I was myself fortunate enough to ob- 
serve a movement of this sort during the 
autumn of 1888; between nine and ten 

* Can. £nt.^ zvii. 204. 

Its Vagrancy, 51 

o'clock in the morning of September 2, 
while sitting on the piazza of a house 
facing the sea-shore at Hampton, N. H., 
and only a stone's throw from the water, 
a continuous stream of these butterflies 
passed before me toward the southwest, 
following the line of the sea-coast, with 
the wind about northwest There were 
never less than three or four directly in 
front of me, often a dozen or twenty. In 
the hour that I watched them, I calcu- 
lated that at least fifteen hundred passed 
me, and without exception in the same 

As flocks also occur in Florida, it seems 
highly probable that the southern move- 
ments may extend over the entire United 
States, and that the northern limit of the 
returning hibernators may be the limit 
within which the butterfly is double- 
brooded. As Riley, the first to suggest 
an annual migration of this butterfly, 
remarks : '' There is a southward migra- 
tion late in the growing season in congre- 

52 The Life of a Butterfly > 

gated masses, and a northward dispersion 
early in the season through isolated 

Another fact in support of this theory 
is that no one has ever found a butterfly 
of this species in hibernation, while there 
is hardly a single one of our butterflies 
which hibernates in the perfect stage of 
which there is not some record of its 
having been found ; and yet our Milkweerd 
Butterfly is nearly twice as large as any 
of these, and would therefore be more 
readily noticed; and if it hibernates, 
would naturally seek just such spots as 
are sought by them. It is by no means 
improbable, then, that in the winter 
the species does not exist north of, say, 
latitude 31°. 

In further support of the theory may 
be mentioned its observed remarkable 
powers of flight, and particularly its com- 
mercial extension in recent years, which 
forms a chapter in its history quite ex- 
ceptional in a butterfly; for within thirty 

Its Vagrancy. 53 

years, or a little more, it has begun to 
invade so many regions of the world as 
to make one think at first blush that it 
may some day vie with Vanessa cardui 
in cosmopolitan character. The facts 
concerning its exotic distribution, so far 
as I have been able to gather them, are 
as follows. 

It first reached the Hawaiian Islands, 
fully two thousand miles distant from 
America, some time not far from 1845 to 
1856. At any rate we have the direct 
statement of Rev. Luther H. Gulick, who 
was born upon the islands, that in 1852, 
after eleven years* absence, he returned 
to the islands, and his brother drew his 
attention to the fact that Asclepias had 
been introduced during his absence, and 
had already become a troublesome weed ; 
that his brother had noticed that wher- 
ever the milkweed appeared, there also 
the Milkweed Butterfly made its advent, 
a butterfly unknown until after the milk-, 
weed had been introduced. 

54 Tb^ Life of a Butterfly. 

We next find it in 1857 as far away 
as the Island of Ponape, in the Caroline 
Islands of Micronesia, a distance of 
another two thousand miles or so from 
the Hawaiian Islands. This fact we also 
owe to Dr. Gulick's personal testimony. 
He was for some time a resident of 
Ponape, and the butterfly was first seen 
by him in the year mentioned, not long 
after he had discovered several young 
milkweeds, which had sprung up in earth 
in which various other plants had been 
brought from the Hawaiian Islands in a 
Wardian case. The plants were brought 
in a missionary vessel which sailed from 
Honolulu, and on its way to Ponape 
touched only at Apaiang of the Gilbert 
Islands and Ebon of the Marshall Group, 
both low coral atolls, and at Kusaie, which 
is of basaltic formation and richly clothed 
with verdure, but where the butterfly did 
not then occur. It is evidently impossible 
that in a voyage consisting in the whole 
of fifty-four days, the insect in any stage 

Its y'agrancy. 55 

or stages could have been transported in 
the Wardian case itself, for it easily un- 
dergoes all its transformations in warm 
regions in a month or five weeks at 

If the butterflies were introduced at 
that time, as there is every reason to 
believe from Dr. Gulick*s accounts, there 
seems no other supposition possible than 
that an impregnated female flew into the 
hold of the vessel while lading at Hono- 
lulu, and was carried perforce to Ponape ; 
or possibly a pair of butterflies. It would 
certainly be absurd to suppose that a 
gravid female could have flown over two 
or three thousand miles of ocean, and in 
addition have appeared on Ponape Island 
almost simultaneously with a few plants 
of Asclepias. As the butterflies live 
through the entire winter and then lay 
eggs in the spring, there is nothing in 
any way really surprising in Dr. Gulick's 
statements, unless it be impossible for an 
impregnated female to live in enforced 

56 The Life of a Butterfly. 

hibernation a couple of months without 
laying ; when it would be necessary to 
suppose a pair to have been transported, 
which would of course be more strange. 

Granting our explanation to be just, it 
is highly probable that it was from this 
single ancestor (or pair) that the swarms 
which have now spread over the entire 
South Seas, in many of which it is the 
commonest butterfly known, have sprung. 
Our knowledge of the period and extent 
of this later distribution we owe largely 
to Professor Semper, who states that the 
butterfly was first seen in 1863 by Captain 
Rachan, one of the numerous collectors of 
the Museum Godefroy, on the islands of 
the Tonga or Friendly group, again nearly 
another two thousand miles from Ponape. 
The first specimen actually obtained was 
secured in 1866 on Niuafau, one of the 
islands of this group; and in the same 
year caterpillars were discovered on As- 
clepias curassavica^ a plant now spread 
quite as far as the butterfly. 

Its Vagrancy. 57 

We now begin to be able to record in 
part the rapidity of its spread, for it was 
first seen in Tutuilla, one of the islands of 
the neighboring Samoan group, in 1867; 
but upon Upolu and Savaii, islands of 
the same Samoan group, distant at the 
nearest some fifty miles, not until 1869. 
Yet in Upolu it became one of the 
commonest butterflies in 1870. It was 
not until 1868 that it was discovered at 
Tongatabu, one of the southern of the 
Tonga Islands, but in the same year it 
was seen in the open sea five hundred 
nautical miles to the southeast In 1869 
it had appeared at Rarotonga, one of the 
Hervey Islands, five hundred miles or 
more away. In 1870 to 1872 it was found 
on Huahine and Tahiti of the Society 
Islands, again five hundred miles or more 

So far the account of Professor Semper. 
But Mr. James J. Walker, who sailed in 
the South Seas in 1883, and nearly 
everywhere found this one of the com- 

5 8 The Life of a Butterfly. 

monest butterflies, states that he was 
informed at the Marquesas Islands (which 
lie to the northeast of the Society Isl- 
ands, again at the distance of some five 
hundred miles), by a Roman Catholic 
missionary residing there forty years, that 
he distinctly remembered seeing the first 
specimen there about the year i860; it 
should be noted that the Marquesas Isl- 
ands are nearly as distant in a southeast- 
erly direction from the Hawaiian Islands 
as the Carolines are to the southwest 
Mr. Walker also found the butterfly on 
the Hervey and Society Islands, and at 
Oparo, one of the Andaman group, in 
28** south latitude, though it had not 
then reached Fitcairn Island, which lies 
much farther east and somewhat farther 

These statistics indicate its movements 
from the Caroline Islands, in an easterly 
and southeasterly direction, but it has 
also left its marks by the way, in a south- 
ward extension from this route of travel 

Its yagrancy. 59 

For it has reached Waigiou, New Britain, 
New Ireland, New Guinea, the Louisiade 
Islands, every part of the Solomon and 
New Hebrides groups, the Duke of York 
Island, the Loyalty and Fiji Islands, New 
Caledonia, Norfolk Island, the northern 
island of New Zealand,^ the entire east- 
ern coast of Australia, from Cape York 
southward even as far as Hobart Town 
in Tasmania. It reached Lord Howe's 
Islands in 1870; Clarence River, on the 
opposite coast of Australia, in 1871 ; Mel- 
bourne in 1872, and has now extended 
even to Celebes, and according to Kirby, 
to Java. 

It thus appears that it now possesses 
a territory in the Pacific Ocean of at 
least 1 10° of longitude and 65^ of latitude. 
But this is by no means all; it has 
moved also in some strange way in the 
opposite direction from the American 
continent. It has long been known at 
Bermuda as one of the extremely few 
butterflies to be found on that island. 

6o The Life of a Butterfly. 

Specimens now in the collection of 
Messrs. Godman and Salvin were taken 
in 1864 on the islands of Fayal and 
Flores, but it seems not to have been 
since recorded at the Azores- In 1877, 
however, it made its appearance on the 
continent of Eurqpe at La Vendue, on the 
Atlantic coast of France, and a number 
of instances of its capture in England 
have since been signalized. These in- 
stances are so numerous, and recorded 
for so many different years, that it would 
seem highly probable that the butter- 
fly has been endeavoring to maintain -a 
foothold ever since 1876, when the first 
instance of its occurrence was recorded. 

The first specimen was found at Neath, 
in South Wales, in September ; a second 
one in Sussex in the same month, and a 
third at Hayward's Heath in October. In 
1877 one was taken at Poole Harbor. It 
did not appear again till 1881, when a 
specimen was taken in Kent in September. 
Again in 1884, one was taken in the Isle 

Its yagratwy. 6i 

of Wight. In August and September, 
1885, niiie specimens were taken in the 
counties of Dorset, Devon, Cornwall, and 
the Isle of Wight. It was again taken in 
1886 in the south of England, in Guern- 
sey, at Gibraltar, and in Portugal. 

I have spoken of this extension of its 
natural region as one due to commercial 
agencies, because it would seem that the 
distance to which the insect has been 
carried must be due to something more 
than its very remarkable powers of flight. 
The fact that the butterfly has been seen 
flying at sea an immense distance from 
land is a sufficient proof of the latter, 
and we should be far from questioning 
its power to compass with no very great 
difficulty one-half the extreme distances 
to which we know it has been carried 
without power of alighting. But that this 
should occur with a female heavy with 
eggs, or twQ individuals together, male 
and female (and no other supposition 
would permit us to understand its subse- 

62 The Life of a Butterfly. 

quent propagation in the regions visited), 
is past credence, — more especially as we 
have in the instance of its spread from 
the Hawaiian Islands to the Caroline 
group an almost certain proof of the 
method of its transport, through artificial 
aid. The alighting of one of these but- 
terflies laden with fertile eggs upon some 
part of a vessel or within its hold would 
be a strange but by no means impossible 
occurrence; and this is all that is neces- 
sary to explain its transport over the 
wider regions. 

That having once established itself in 
one of the Micronesian Islands, it could 
easily spread over the whole of Polynesia 
through the insect's natural powers of 
flight, will hardly be questioned. But 
that this has taken place not only within 
historic times, but within the last twenty 
or thirty years, as has been shown by 
Semper, makes it almost certain that its 
first introduction to the South Seas was 
by artificial means; for if it could have 

Its Vagrancy. 63 

been brought about solely by the powers 
of flight of the insect, aided by the nat- 
ural currents of the air, it would have 
happened long ago ; and the facts that the 
insect has been able to establish itself 
wherever it chose when it got a foothold, 
and that until a very recent period it 
has not so established itself, are sufficient 
proofs that commercial agencies, so much 
more abundant in later times than for- 
merly, have been the great means of in- 
troducing these butterflies to the islands 
of the Pacific. It is highly probable 
that it owed its first introduction to the 
Hawaiian Islands to similar agencies, and 
that its appearance in Europe is due to 
the same cause. 

This is all I have now to say of the 
theory here advanced, that the butterflies 
of this species found annually in the 
northern United States and northward 
must be regarded as a wave of migrants 
from the south which have come north 
like the birds to breed, after which their 

64 The Life of a Butterfly. 

young return, or if they fail to do so, 
perish. What after all is this but an 
exaggerated case of the perpetual flux 
which has been going on with all our 
Northern butterflies ever since at least the 
glacial epoch? There were certainly no 
butterflies here when the country was 
flooded with ice, and all that have since 
appeared are but immigrants from the 
South ; and at the northern limits of their 
distribution there have no doubt ever been 
a continual struggle and an ebb and flow 
of life as a severer winter or an exces- 
sive drought destroyed the species in toto 
over a certain range, replenished later by 
migrants from the border. 

In short, the present distribution of life 
is the result of the constant attempt of 
every species to extend its territory, to 
gain more room to live, the outcome of 
the balance of forces which have held all 
in restraint And though our Milkweed 
Butterfly presents phenomena in its dis- 
tribution of ^n apparently exceptional 

Its Vagrancy. 6$ 


kind, showing it to be an unusual vagrant, 
it is probable that any species we might 
select for discussion would in the last 
analysis serve equall> well to show how 
the struggle for room to live in has been 
but one phase of the ever-present struggle 
for existence. 


The Critical Periods of its Life. 

OW-A-DAYS it is not necessary 
to insist upon "the struggle for 
existence;** popular literature has 
made it a household phrase. Every crea- 
ture, all its life long, may be said to be 
subject to the bondage of danger and 
fear ; and every creature is furnished with 
structural or physiological resources to 
meet danger. Still, there are in the lives 
of the lower animals, as well as of man, 
certain critical periods when more than 
at others they are liable to destruction. 

Although through most of its life pro- 
tected to a certain extent, as we shall see, 
by its noxious qualities, I see no reason 
to suppose that in its egg state the Milk- 
weed Butterfly is not subject to the same 
decimation to which I believe all or nearly 

The Critical Periods of its Life. 67 

all butterflies are doomed. From my 
experience (not very extended) in observ- 
ing eggs of butterflies laid in the free air, 
I should indeed judge that decimation 
was rather a feeble term to apply to the 
destruction of egg life. I have in fact 
seen spiders at their meals upon them; 
and Mr. W. H. Edwards, speaking of the 
Violet-tip, Polygonia interrogationis^ once 
wrote : — 

'' When it is considered how many eggs are 
laid, and that so short a time intervenes be- 
tween the egg and the imago^ it is surprising 
how few butterflies of this species are the 
result. From eggs that were laid on my vines 
in July and August, amounting I am sure to 
many hundreds, very few larvae were hatched. 
. . . The eggs are destroyed by spiders and vari- 
ous insects by wholesale. I have had the con- 
tents of one of my [breeding] kegs swept away 
in a night, leaving not a trace of shell behind." 

Not a few eggs, too, are eaten dry by 
minute parasitic Hymenoptera so small 
as to look like mere grains of dusL .Lit*. 

68 The Life of a Butterfly. 

tie attention has been paid to these by 
naturalists, but from my fortune with 
eggs I have found in the open air and 
attempted to rear, a good tenth must be 
ruined in this way ; they will even invade 
the muslin net under which eggs are laid 
by butterflies in captivity, and pierce 
them. Among the dozen and a half of 
our butterflies whose eggs have been 
actually found so pierced, the Milkweed 
Butterfly must be counted. If, then, any 
possible noxious qualities in the egg are 
of no avail against that speck of dust 
the Trichogramma, spiders and crickets 
are not likely to eye it askance. It is 
highly probable with this butterfly, as it 
is certain with many others, that the egg 
is the most perilous period of its life, one 
whose mortality will show the greatest 
percentage of loss to the species. 

To counterbalance this, the egg state 
is usually the shortest of any of the four 
the saved remnant are to pass. In the 
Milkweed Butterfly, its duration does not 

The Critical Periods of its Life. 69 

exceed three or four days. It is very 
rarely less than that in any butterfly, 
even in the hottest season or region, but 
is sometimes prolonged considerably ; and 
curiously enough, this is particularly the 
case in those same species in which the 
larval stages are also prolonged, as if a 
certain inertness belonged to the whole 
life. In view of the dangers to the egg, 
the fact we have already mentioned, 
that some species winter solely in the 
egg state, is not a little surprising. It 
should be noted, however, that with almost 
no exception, the species of temperate 
regions known to winter in the egg belong 
to the gossamer-winged butterflies, the 
Lycaeninae, the shells of whose eggs are 
as a rule of exceptional thickness; and 
the same is true (or the eggs are very 
coarsely ribbed) in every known case 
outside this group, with a single published 
exception, which I believe erroneous.* 

* Coenonympha pamphilusy said by Assmuss to winter 
in western Russia in the egg. This butterfly is double- 

70 The Life of a Butterfly. 

Small as it is, the newly hatched cater- 
pillar has almost equal peril, and from the 
same larger enemies — spiders, cricTcets, 
and bugs — which have threatened the 
egg. Edwards, in the passage quoted, 
adds : " And in the same way I have 
lost scores of small larvae." It is highly 
probable, as suggested in a previous chap- 
ter, that this is the reason why the young 
caterpillar ordinarily devours nearly ot 
quite all the shell it has left the moment 
it enters upon free life ; for by removing 
this indication of its proximity, the cater- 
pillar indulging in such a propensity is the 
more likely to live to leave descendants, 
and thus a habit may become fixed. But 
it is perhaps in greater peril, because to 
obtain its food it rtiust move, and a 

brooded in England, — the first brood appearing, ac- 
cording to Buckler, in May, impossible to have come 
from a wintering egg ; indeed one instance is on record 
of pupation on April 5. It is double or triple brooded 
in Silesia, according to Prittwitz, and the caterpillar is 
full grown at the beginning of May. It must surely 
hibernate as a caterpillar, as Schwartz claims. 

The Critical Periods of its Life. j i 

moving object, especially to insect vision, 
is more apparent than one at rest. It 
satisfies its appetite therefore at the risk 
of its life, and after its meal remains 
rigidly still. 

It is probable, however, that it is at its 
next stage, after once moulting, that the 
caterpillar's danger is at its greatest. For 
with its growth in size, it has now become 
a mark for a new class of enemies, the 
ichneumon flies and tachinid flies, which 
nourish their young within its body. 
Our Milkweed Butterfly is certainly more 
exempt from danger from them than is 
perhaps any other of our native species, 
and was long thought to be totally free 
from them, but we already know of two 
kinds of four-winged ichneumon flies — 
a larger and a smaller — and one kind 
of two-winged tachinid flies which prey 
upon it. 

I believe that it is at this early stage in 
their life that caterpillars are ordinarily 
stung, giving the worms hatched within 

^2 The Life of a Butterfly. 

time to prey their life long upon the 
nourishment meant for the bodies of their 
hosts. How often caterpillars taken at 
large and brought to the breeding cage to 
rear yield these concealed villains, only 
those who have tried it realize; nor how 
many such harpies may be carried within 
one. caterpillar and the caterpillar still 
thrive, — a peripatetic banqueting hall for 
unbidden guests! 

When larger the caterpillars have the 
birds, and if they be low feeders, the 
reptiles to contend with ; but though one 
of our ornithologists says he has found 
the caterpillars of our commonest yellow 
butterfly in the stomachs of as many as 
twenty different kinds of our native birds, 
it is not probable that the destruction by 
birds is nearly as great as by insect foes. 
Against the birds they have only their 
form and color to oppose, through which 
by their resemblance to their surroundings 
or to some uneatable object they may 
escape detection or be left undisturbed; 

The Critical Periods of its Life. 73 

and this resemblance is often more strik- 
ing than one would believe, seeing them 
shut up in a naturalist's box or prepared 
for the cabinet. To gain any conception 
of it one must see them, if he can, in their 
natural haunts, and he will discover either 
how hard they are to find or what grotesque 
or inanimate things they appear to be. 

This is not at all the case with the 
subject of our sketch, for the plump cater- 
pillar of the Milkweed Butterfly, though 
when at rest it usually conceals itself 
beneath a leaf to which it clings upside 
down, is a most conspicuous object, with 
its transverse belts of black upon a 
white and yellow or orange ground; but 
in this case, and probably in a few others,^ 
such as the almost equally conspicuous 
caterpillars of our Swallow-tails, we are 
brought into that class which owes its 
immunity to attack to the nauseous quali- 
ties of its members, which these " warning 
colors" by their very conspicuousness 
appear to proclaim. 

74 The Life of a Butterfly. 

One would think, at first, that one 
danger to caterpillars might be in finding 
proper food supply, especially if it were 
known how very particular many kinds of 
caterpillars are, — starving to death unless 
they can find the single species on which 
they feed. Doubtless this is an occasional 
cause of death. I once found several 
eggs of Anthocharis geniUia on a slender 
Arabis which would not have yielded 
enough nutriment for one caterpillar, and 
after an hour or more of search — and I 
was very eager to find more eggs — could 
not find another stalk of that or any 
similar cruciferous plant (on which alone 
the caterpillar is supposed to feed) within 
an area of several acres. But such cases 
are rare, and it is to the parent the credit 
is to be given, who with careful search 
almost invariably selects the very choicest 
;pots for the progeny that shall spring 
•om her eggs. 

A A more obvious danger is to be found 
in the necessity for those repeated slough- 

The Critical Periods of its Life. 75 

ings of the skin which its growth neces- 
sitates; at such times the caterpillar is 
completely helpless, generally incapable 
of more than a feeble wriggle, and 
continues in this condition for hours, 
sometimes for days at a time. Sometimes 
it seeks special concealment for the 
change, but in a great many cases, strange 
as it seems, ecdysis occurs in plain sight 
of all, upon the surface of a leaf; it has 
then only its immobility to protect it. 

A similar critical period is found during 
the change to chrysalis, which generally 
occupies a day or two; this frequently 
occurs under protection of some con- 
cealment, though this is less often the 
case among the brush-footed butterflies, 
to which our milkweed species belongs, 
than with others. But when the change 
has taken place and the at first flabby 
chrysalis has gained its form and color, the 
matter at most of but a few hours, there 
is rarely an instance where resemblance 
or color-harmony with its surroundings 

^6 The Life of a Butterfly. 

is not a very effective protection ; and in 
many the angularities of the surface, like 
the spines of many caterpillars, may be 
an additional source of safety. It would 
seem, indeed, that having fairly reached 
the chrysalis state, there was relatively 
little danger until it was upon the wing. 
It is true that many chrysalids give forth 
not the butterfly, but two-winged or four- 
winged parasites, but these are a legacy 
from the caterpillar and not an independ- 
ent production ; these insect parasites are 
not known to sting the chrysalis.* 

It is usually but a meagre remnant 
that passes through all these stages to 

* I had supposed this to be absolutely true, but 
Howard, in his excellent account of the biology of one 
family of these parasites (Proc. U. S. nat. mus., xiv. 
569), says: ''The pupa [of LepidopteraJ itself is sel- 
dom attacked, yet certain of the Pteromalines which 
preferably oviposit in larvae about to transform will 
also lay their eggs in just-formed pupae. The same is 
the case with certain members of the genus Chalcis, 
particularly those parasitic upon diurnal Lepidoptera, 
and I am not sure that C.flavipes does not oviposit by 
preference on the fresh chrysalids of CMorippe clyton 
and Agraulis vanillae" 

The Critical Periods of its Life. y/ 

finally attain the winged state. Probably 
in the Milkweed Butterfly the remnant is 
exceptionally large, but with the mass of 
our butterflies it seems extremely doubtful 
whether five per cent of the embryos 
which are deposited in their egg-shell 
ever attain their majority ; and when these 
have gotten them wings and fly away, 
new dangers interpose. There must be 
more or less delay about laying the eggs ; 
in many species the eggs are not ripe to 
lay for several days, in some apparently 
not for weeks; suitable places must be 
chosen, and in nearly all instances the 
eggs must be laid one by one, and aref 
laid on diflerent plants; all of this of I 
course takes time, and only in sunshine 
can they or do they so occupy themselves. 
Meanwhile there come the storms which 
destroy them in large numbers, and the 
birds which snatch them up; especially 
do the more sluggish females suffer, heavy 
with their burden of eggs. It seems quite 
safe to say that not one half the possible 


78 The Life of a Butterfly. 

eggs of a given brood of butterflies ever 
get laid at all. 

And so it comes about that for every 

pair of butterflies a given season, with its 

1 potentiality of a brood of hundreds, the 

1 next season witnesses but still one pair. 

1 The balance of Nature is kept up. Yet 

\ now and again there are fluctuations, beats 

of the biologic pendulum. One year vast 

numbers of one kind are seen, which 

was scarce or almost not to be found the 

very year before. This is probably to be 

explained by the fact that their scarcity 

the first year meant paucity of food 

to their parasites, which consequently 

starved, and were not present in suflicient 

force the second year to make their usual 

inroad upon their numbers. Just so does 

the entire animal world show a struggle 

between herbivore and carnivore for the 

occupation of the ground. " Increase and 

multiply " is the primal law of each. 


A Favored Race : Mimicry and Protective 


ILEY tells us that in Missouri 
the tachinid parasites of the 
Milkweed Butterfly, its most 
meddling insect foe, are sometimes so 
active that not one in fifty of the 
caterpillars escape them; yet it will, I 
think, be agreed by all observers that as 
compared with the caterpillars of other 
butterflies it enjoys a very considerable 
immunity. Is it possible that this is 
simply because it is not attacked by 
birds or toads? Its "warning" colors, at 
any rate, are more likely to be the result 
of immunity from the attack of vertebrate 
than of insect foes, and the former are of 
a relatively greater importance in the 

8o The Life of a Butterfly. 

tropics, which it must not be forgotten 
is the real home of this insect, than in the 
temperate region. 

Nor should it be overlooked that the 
three most striking insects which — in New 
England at least — ordinarily accompany 
the caterpillar upon the milkweed, the 
caterpillar of the moth, Etichaetes egle, 
the longicorn beetle, Tetraopes tetraoph- 
tkalmuSy and the chrysomelid, Doryphora 
clavicolliSy are equally conspicuous and 
have similar coloring, a contrast of black 
and orange in broad markings. Have 
they, perchance, gained these colors by 
unconscious mimicry? Why should four 
such striking insects with similar colors 
preponderate upon the milkweed? 

However this may be, — whether or no 

the gayly banded caterpillar and the gold- 

and-black-dotted pea-green chrysalis of 

the Milkweed Butterfly are specially pro- 

itected from vertebrate foes, there can 

\ be no doubt that this is the case with the 

erfect butterfly. Indeed all the members 

! U 



A Favored Race. 8i 

of this group of insects the world over, 
so far as known, have a more or less 
rank, in our species a carroty, odor; and 
some of them contain a pungent fluid 
which will exude under pressure and stain 
the skin. They are evidently malodorous 
or nauseous to birds, and their easy 
movements on the wing are an added 
proof that they are rarely or never then 

One observer in Brazil, watching a pair 
of puff birds catching butterflies to feed 
their young, noticed that the butterflies 
of this group were never attacked, though 
flying lazily about in great numbers. 
Their abundance wherever found — and 
they frequently swarm — is another silent 
evidence of their safety on this score; 
and since the statement was first made, 
thirty years ago, that they were probably 
proof against attack on the ground of 
their unpalatableness, it has, I believe, 
never been denied by any observer, and 

has been so many times verified and con- 


82 The Life of a Butterfly. 

firmed that there is now general consent 
to the proposition. 

But this is only the beginning of the 
matter. Here again we meet with the 
old story of ** the struggle for existence." 
Life is such a warfare that artifice and 
deceit are to be looked for on every 
hand. Given a favored race, it will be a 
gain to their unfavored persecuted friends 
to resemble one of them, and so a prize — 
the prize of a better hold on life — is 
offered for a forgery. It was an as- 
tonishing fact that was brought to light 
by Bates, — that a group of butterflies 
occurred in Brazil of vivid coloring and 
slow and easy flight, which were the 
constant subjects of mimicry by butterflies 
of quite a different type, normally white 
and tolerably uniform in color, but which 
had so changed their livery, and even the 
form of their wings, as closely to resemble 
the objects they mimicked in brilliancy 
of color and variegation, and even in 
mode of flight 

A Favored Race. 83 

Some, says he, "show a minute and 
palpably intentional likeness which is per- 
fectly staggering." Indeed, the likeness 
proved so close that even after he became 
aware of the mimicry his practised eye 
was often deceived. Or if he wandered 
to a new locality, where occurred a new 
set of Ithomyiae (the most numerously 
represented among the mimicked genera), 
the Leptalides (the mimickers) , would 
vary with them so as to preserve the 
mockery, band for band and spot for 
spot. It is now known that wherever 
these protected butterflies are found, the 
world over, they are accompanied by a 
set of mimicking forms of some totally 
different group. We have in our own 
country two such instances of a con- 
spicuous kind, one species of Basilarchia 
(Nymphalinae) mimicking Anosia plexip- 
pus (Euploeinae), and another species 
of Basilarchia mimicking Tasitia berenice 

The fact of a resemblance so close that 




84 'the Life of a Butterfly* 

it is to all appearances a "palpably in- 
tentional likeness" is impossible to ques^ 
tion. But how explain it? How can a 
butterfly change its appearance to such 
a degree? **Can the Ethiopian change 
I his skin or the leopard his spots?" 

The answer, as Bates clearly saw, was 
to be looked for in the same direction 
as when accounting for the assumption 
by animals of the color of their surround- 
ings. Both . are produced in the same 
way, and have the same cause and end. 
It is only by keeping in view this tolera- 
bly obvious truth that we can explain all 
the freaks of mimicry. **The specific, 
mimetic analogies," says Bates, " are 
adaptations, — phenomena of precisely 
the same nature as those in which insects 
. . . are assimilated in superficial ap- 
pearance to the vegetable or inorganic 
substance on which or amongst which 
I, they live." 

To gain an idea, then, of the processes 
by which the " staggering " examples of 

A Favored Race, 85 

mimicry are produced, we must look first 
at the simplest forms of protective resem- 
blance. Go to the seashore and observe 
the grasshoppers among the beach grass. 
They fly up at your approach, whiz off a 
rod or so, and alight. Can you see them ? 
They are colored so nearly like the sands 
they live upon that detection of one at 
rest is almost impossible unless one has 
seen it alight. On yonder grassy bluff, 
a stone's throw away, you will find none 
of them, but other kinds equally, or 
almost equally, lost to sight by their 
harmony with their surroundings. What 
chance of life for either if they suddenly 
changed places? They would be so con- 
spicuous that every passing bird or other 
insectivorous creature would sight them. 

Of course these protective colors have 
been gained by very slow steps. Every 
grasshopper that lived by preference 
among the sands was liable to be eaten. 
In the long run just those would be eaten 
which were most easily seen. One which 




86 The Life of a Butterfly. 

varied in coloring in never so small a 
degree, so as to be less easily seen than 
his brother, would live to perpetuate his 
kind, and his brother would come to an 
untimely end; the progeny would show 
the fortunate variation, and be more likely 
to be spared to transmit in increased 
volume the probability of the happy 

Given, then, a brood of grasshoppers 
that find their preferred food in sandy 
spots, and unless other and more powerful 
forces act upon them, it must result, from 
their liability to be eaten by creatures 
fond of grasshoppers, that in time they will 
resemble in coloring the sand on which 
they live, — it is impossible that they 
should not. Any creature not specially 
protected by nauseousness or habit or 
special device of some sort must in the 
very nature of things, if it is to live at 
all, have some other protection ; and that 
afforded by color and pattern is by far 
the most common. The world is made 


A Favored Race. 87 

up of eaters and eaten, of devices to catch 
and devices to avoid being caught. 

We may apply the same reasoning to 
two kinds of butterflies subject naturally 
to the same class of enemies; that is, 
living in the sanie region and flying at 
the same time. If one has the slightest 
advantage over the other in the fight for 
life, by being, for instance, distasteful to 
one class of common enemies, so that 
these forbear to attack it after experiment 
or by instinct (the result of ancestral ex- 
periments), and there be among the less 
favored flock, here and there, an individual 
which, under circumstances favoring it, 
such as distance or shadow, may more 
often than its fellows be mistaken by the 
enemy for one of its distasteful neighbors 
through its possession of a little more 
than usual of a certain tint on a part of 
the wing, a little larger spot here, or more 
of the semblance of a band there, — how 
small soever this 'difference may be, it 
must, by the very laws of natural selection, 


88 The Life of a Butterfly. 

be cherished, perpetuated, increased, by 
slow but sure steps. Nor is there any 
limit to its increase except its absolute 
deception of the enemy. So long as there 
is the slightest advantage in variation in 
a definite possible direction, the struggle 
for existence will compel that variation. 
Knowing what we now know of the laws 
of life, mimicry of favored races might 
even have been predicted. 

It would seem, then, to be plain that all 
cases of protective coloring and mimetic 
form come under one and the same law, 
and have been produced by the same 
means (the survival of the best mocker), 
whether the object imitated be animal, 
vegetable, or mineral. The actual out- 
come is, indeed, vastly more surprising 
in some cases than in others, — in some 
" perfectly staggering," as Bates says ; yet 
though there be to all appearances a 
"palpably intentional likeness," there is 
! found to be no intention in the case so 
f far as mocker aiid mocked are concerned. 

A Favored Race. 89 

but the result of a natural selection against 
which neither could even strive, and of 
which neither was ever conscious. 

The process has been a long one, so 
that in the case of parastatic mimicry, as 
that form which involves the copying of 
one's fellows might be termed (or if 
one prefers an English term, neighborly 
mimicry), we may readily presume far less 
difference between mocker and mocked 
when the mimicry between them first 
began than now exists between the 
mocked and the normal relatives of the 
mocker. It is argued, indeed, with great 
show of reason, that as the resemblance 
grew stronger the birds became more 
sharpsighted, which reflected again on the 
mimicry, and that thus the final departure 
from the normal type was intensified ; but 
this assumption is not necessary. 

It is to be presumed that the actual 
colors found in a mimicking butterfly 
are, with rare exceptions, such as existed 
somewhere in the ancestral form. In the 

go The Life of a Butterfly. 

case of our own mimicking Basilarchia, 
for example, whose orange ground tint 
is so totally at variance with the general 
color of the other normal members of 
the group, it will be observed that all 
the normal species possess some orange. 
Without this as a precedent fact, such 
perfect mimicry might perhaps never have 
arisen. Individuals among the normal 
species vary somewhat in this particular, 
so that it is easy to suppose that some 
of the original B. archippus^ with more 
orange than usual, may have escaped 
capture, on occasion, from this cause. 
From such a small beginning, such as one 
may now see every year in B, astyanax, 
sprang doubtless the whole story, and at 
last we have a butterfly which has for a 
ground color of both surfaces of the wings 
an orange which is the exact counterpart 
of that of Anosia plexippus; by reason 
of which, in all probability, it enjoys a 
freedom from molestation comparable to 
that attributed to A. plexippus^ so that it 

A Favored Race. 


ventures more into the open country than 
its allies, and thus gains a wider pasturiige 
and surer subsistence. 

It is not necessary for our purpose to 
enter here into further details about the 
various forms and phases of mimicry;* 
it is sufficient to point out that in some 
instances only one sex, and that the 
female, departs from the livery of its kind 
to mimic that of its pattern; that in 
others a normal male of the mimicking 
group may have several forms of female, 
one mimicking one, another another, of 
the protected type; that some butterflies 
of the protected group are mimicked by 
others within the same group; and that 
butterflies of other than the protected 
group are the subjects of mimicry. 

Of this last we have one of the most 

* Those wishing to pursue this matter further are 
referred to my paper on the subject in the Atlantic 
Monthly for February, 1889, printed also in my "Butter- 
flies of the Eastern United States," as Excursus xxiii. 
pp. 710-720, to which latter will be found appended a 
bibliography of the subjects 

92 The Life of a Butterfly ^ 

curious cases in our own country. One 
of^our fritillaries, Semnopsyche diana^ is 
remarkable for the great difference in 
coloring between the male and the female : 
the male would be taken at once for a 
fritillary from the general tone of color- 
ing both above and below; but at first 
glance one would say the female was a 
Basilarchia (a butterfly of quite a different 
tribe), from its close resemblance to B. 
astyanax. Indeed, when first seen alive 
by Edwards, then on the hunt for the 
species and ignorant of the female, he 
actually thought it a species of Basilarchia 
near B. astyanax. Its range in the South, 
too, is completely covered by that of 
B. astyanax. 

The fact of mimicry in this instance 
must be regarded as unquestionable; but 
the strangeness is the greater that in our 
country it is just in this genus Basilarchia, 
here mimicked, and in no other, that 
striking mimicry of the ** favored tribe " 
occurs. It is a case somewhat parallel to 

A Favored Race. 93 

mimicry within the favored tribe, but the 
more striking that the cases mentioned 
stand alone among all the American 
genera. Mimicry is far more common 
(even relatively) in the tropics than in 
the temperate regions; so, too, are in- 
sectivorous animals. And it should be 
remarked that if we are correct in our 
opinion that our Milkweed Butterfly is, 
in the strictest view of the matter, an 
autochthone in our country only in the 
extreme South, then it is easier to explain 
the mimicry of Basilarchia, for there 
would not seem to be any occasion for 
mimicry of B» archippus in the higher 
North. I have myself never seen a. but- 
terfly (but often a moth) pursued or 
snatched by a bird, though I once came 
across the evident signs of capture in the 
scattered wings of Euphoeades troilus on 
a damp roadside where I had just missed 
its coursing back and forth. Mimicry in 
the perfect stage is only needed where 
their vertebrate foes are numerous and 

94 The Life of a Butterfly. 

When we take a general view of mimicry 
as exhibited by one butterfly for another, 
how strange it seems ! and what an inter- 
esting illustration it is of the adaptability 
and pliancy of natural forces that for the 
evident protection of one species in the 
struggle for existence so exact and beau- 
tiful a resemblance should be brought 
about! Consider for a moment that the 
subjects of mimicry are at the final stage 
of life ; they have already passed through 
nearly all the dangers to which the 
species, as a species, is subjected, — so 
rudely subjected that they are a mere 
remnant of those brought into the world 
with them. During the early period of 
their life they were exposed to vastly 
more dangers than they can now experi- 
ence. At times they were absolutely 
helpless, without the power of movement 
They are now endowed with powers of 
flight sufficient to thwart the purpose of 
many a foe; yet it is in just this period 
that these special and extraordinary pro- 

A Favored Race. 95 

visions for their safety — and for the 
accomplishment, so far as the species is 
concerned, of the end of their life — are 
given them. All this has been brought 
about for the sole purpose of prolonging 
their aerial life for the exceedingly few 
days which are necessary for pairing and 
the deposition of eggs. The more we 
contemplate so strange and perfect a 
provision, and the means by which it is 
accomplished, the more are we impressed 
with the capabilities of natural selection, 
and begin to comprehend how powerful 
an element it has been in the development 
of the varied world of beauty about us. 



Scent-Scales : a Question of Sexual Selection 

lERHAPS it will be remembered 
that in describing the Milkweed 
Butterfly in our first chapter, the 
male was said to be distinguished by the 
presence of a small but conspicuous black 
pouch or pocket, like a swelling or blister, 
on one of the veins of the hind wings. It 
is so heavily clothed with scales that we 
hardly notice that it is a pouch, open by 
a narrow slit on the upper surface of the 
wing on the side farthest from the vein 
to which it is attached. What does it 
contain? And what is it for? 

These questions open to us one of the 
most curious, one of the most interesting, 
and yet one of the least studied chapters 
in the life and structure of butterflies. 
The interior of the pouch is filled with 

Scent-Scales. 97 

scales attached to the membrane, of which 
there are two kinds, differing in form and 
in setting: one kind is long oval, with 
uniform margins, and which differs from 
the scales exposed on the surface of the 
wing only in being slenderer and in not 
being toothed or notched at the tip ; the 
other kind, however, can scarcely be 
called scales, for they are more properly 
rods, seated in the centre of little raised 
rings which are quite absent from the 
base of the other scales, whether within 
or without the pouch. The pouch is 
evidently for their protection, and we 
naturally ask what they are for, that they 
should be so carefully guarded. 

To answer this inquiry, we shall have 
to go further afield, and see what other 
butterflies may have comparable with 
these ; and we may well be astonished at 
the revelation that will be forthcoming, 
for we shall discover these singular scales 
in every direction and in every form, 
but usually concealed in major part or 




98 The Life of a Butterfly. 

entirely, either by the other scales or by 
folds of the wing membrane. 

Sometimes they differ but little from 
ordinary scales, or may be lopsided; at 
others, they assume the form of a battle- 
dore and are studded with beads ; in many 
they terminate in a longer or shorter 
fringe of the most excessive tenuity, quite 
invisible without a tolerably strong power 
of the microscope; very generally they 
are exceedingly slender and even then 
may be fringed at the tip; or they may 
assume the form of hairs shaped like . a 
shepherd's crook, or a straight rod with 
a whip-lash at the end; or a twisted 
ribbon or a chain of links; or they may 
be spatulate or even fan-shaped at the 
extremity. The range, indeed, of their 
form is strikingly at variance with their 
concealment and microscopic size, and 
they are infinitely more varied than the 
exposed scales, which are almost always 
toothed or combed at the tip, which. is 
rarely or never the case with these* 

ScenUScales. 99 

They are sometimes scattered more or 
fess sparingly over the upper surface of 
the wings, all but their tips concealed 
even from the microscope by the over- 
lapping of the ordinary scales ; but they 
are generally gathered more or less 
abundantly into clusters on either surface 
of the wings, ordinarily on the upper, in 
definite patches visible as a sort of cloud- 
ing to the naked eye, or along veins 
which they then appear to thicken. In 
nearly all, if not all, of these cases the 
visibility to the eye does not, however, 
result from the multitude of the special 
scales, but from the exceptional develop- 
ment and varying color of the attendant 
normal scales, which are either larger, 
darker, or more opalescent than their 
neighbors, or are raised or turned at an 
angle which catches the eye by the gen- 
eral effect; it is much as if the special 
scales we are investigating were playing 
hide-and-go-seek among the others, cry- 
ing ** here we are " by signs, but still 
hiding from view. 

100 The Life of a Butterfly. 

In other cases these patches are con- 
cealed by being placed where the front 
and hind wings overlap; or, as in die 
case of our Milkweed Butterfly, a special 
membranous pouch is developed for their 
benefit. In one great division of the 
Skippers the membrane of the front 
margin of the fore wing is expanded and 
folded over upon itself, but so deftly that 
it is often hard to see that this is the 
case ; and in many of the allied Swallow- 
tails, the plaited part of the hind wings 
next the abdomen will be found put to 
service in a similar manner; while the 
space within, in both these instances, is 
so crammed with these special scales that 
when the folds are opened the scales may 
be removed en tnasse as a bunch of silken 

The study of these scales has only just 
begun, and the above gives only a faint 
notion of the wonderful variety in form 
and curious disposition so far seen; but 
we have learned one thing at least which 

Scent-Scales. loi 

gives a clew to their meaning and pur- 
pose. They are absolutely peculiar to the 
male sex, just as much so as that whole 
class of structures known as secondary 
sexual characteristics, upon the presence 
of which Darwin bases his theory of 
sexual selection, — the one prime feature 
of his philosophy not subscribed to by 
his colleague in the introduction of the 
modern doctrine of evolution, Wallace. 

On account of this restriction to the 
male sex they have been termed andro- 
conia, or male-scales; and Wallace may 
well employ them as an argument upon 
his side, for while they will not yield the 
palm to other secondary sexual features 
in variety and beauty, they are so placed 
that with the exception of such cases as 
the folds of the hind wings of Swallow-tails 
(the wider expansion of which may open 
the fold and expose the androconia), they 
are concealed either absolutely or all but 
their tips, where at the most nothing but 
a fringe or an edge is exposed, and the 

I02 The Life of a Butterfly. 

size of this so infinitesimally small that 
the wildest adherent of the hypothesis 
of clear vision by insects would hardly 
regard vision as a possible factor in the 

The patches of accessory scales might 
be regarded differently ; but these are not 
always present, and an explanation must 
cover both cases, whence the presence of 
absolutely concealed androconia in as great 
a variety of form and position as that 
of other secondary sexual characteristics 
must be regarded as a fatal blow to 
Darwin's view of sexual selection. Other- 
wise there should be no need of his 
efforts to show how the male displays 
these particular charms to his consort at 
the breeding season. 

But we know more about these andro- 
conia. About fifteen years ago, Fritz 
Miiller, a naturalist who by his researches 
in various fields has done much to bring 
new evidence in support of the theory of 
evolution, astonished naturalists with a 

Scent-Scales. 103 

long list of odors emitted by butterflies 
and moths; and among the sources of 
these odors he claimed various patches 
of scales, which are nothing more nor 
less than those where androconia lie 
concealed, as he has pointed out in a 
series of papers where these are figured 
and termed scent-scales. 

This view of their function has been 
found more plausible since minute canals 
have been traced through certain andro- 
conia, canals which in some cases continue 
through and open at the extremities of . 
the delicate threads which form their 
fringe ; and also since Weismann has 
clearly shown that there is a living tissue 
in the wings which would allow of the 
production of an odor through local active 
scent-glands. Moreover the number of 
instances of aromatic butterflies in which 
the odor is referable to the androconia 
is constantly increasing, although as this 
odor is lost after death, observations on 
this head can only be made in the field. 

104 Th^ ^if^ of a Butterfly. 

A few instances may suffice, all of which, 
it must be remembered, are confined to 
male butterflies. 

Antirrhea emits a strong odor from a 
patch of scales near that part of the 
hind wings, which is covered by the fore 
wings, and which is further protected by 
a curving mane of pale buflf hairs ; a faint 
odor "resembling that of sable fresh 
from the furrier's shop " is given out in 
Stichophthalma by a patch on the hind 
wings accompanied by an erectile wisp 
of hairs; a black spot of scales near 
the base of the under side of the fore 
wings in Didonis gives out a musk-like 

In our own fauna we have a striking 
instance of this odor in the scent emitted 
by the scales clustered along the median 
nervules of the upper surface of the fore 
wing in Argynnis atlantiSy — scales which 
have a distinct odor of sandal-wood, so 
strong that it is hardly possible to handle 
living specimens without recognizing it, 

Scent-Scales. 105 

and which I have kaown to be retained 
for many weeks after death, when the 
insect had been enclosed at capture in a 
paper envelope. This is the more remark- 
able because I have never detected the 
same or any odor in the two allied spe- 
cies of Argynnis of New England, which 
nevertheless possess precisely the same 
scales, and in the same position. Finally, 
we have the instance of our Milkweed 
Butterfly; the scales found in the little 
pouch which we are considering emit a 
slightly honeyed odor over and above the 
carroty smell which all the scales possess. 
All these are instances from a single 
family of butterflies. 

In other families may be mentioned 
our common blue butterfly of the spring, 
Cyaniris pseudargioluSy which has an ex- 
ceedingly delicate odor, which I can only 
describe as that of newly-stirred earth 
in the spring, or of crushed violet stems ; 
our large Callidryas etibule, which has 
a slight violet odor; Melete, where the 

io6 The Life of a Butterfly. 

upper side of the wings, especially if 
parted after having been closed some 
time, gives a rather faint but " very deli- 
cious perfume ; " our white butterfly, 
Pieris oleracea, where a faint odor of 
syringa blossoms may be detected; the 
European P. napi, said by different writers 
to have the odor of thyme, verbena, 
orange, or balsam; Papilio polydamaSy 
which, according to Miiller, has "two 
sets of males emitting equally strong 
but quite different odors," — a case of 
diosmism ! 

These instances, with the many others 
known, clearly prove that very many but- 
terflies emit odors, apparently in most 
cases agreeable to us, which it is in 
the highest degree probable are emitted 
through microscopic canals, which course 
through microscopic scales to micro- 
scopic glands at their base within the 
wing membranes ; that while these are in 
some cases easily perceptible by man, he 
is unable to detect any odor whatever in 

Scent-Scales. 107 

their very next neighbors, which possess 
the very same apparatus. The only ex- 
planation of this which appears plausible 
is that odors exist imperceptible by us 
but perceptible by them, an explanation 
which .requires us to attribute to these 
insects an exceedingly delicate and high 
perception of odors. 

This requirement will hardly appear to 
present the remotest difficulty to persons 
who have witnessed what is termed the 
" assembling *' of moths ; that is, the habit 
of the males of many species, notably 
of the Bombycidae, to collect in swarms 
around a female that has been disclosed 
from its cocoon entirely out of sight of 
and often at a great distance (sometimes 
miles) from her visitors, — in a dwelling, 
for instance, in the middle of a great city. 
Instances of this sort are numerous and 
well known, and compel us to admit a 
power or a delicacy of sense perception in 
the direction of smell which opens the 
door to many mysteries in the under- 

io8 The Life of a Butterfly. 

standing of the lives of these humble 
creatures ; they do not so much ** walk 
by sight" as fly by smell! 

This, then, is the probable function of 
all these androconia, as we know it to be 
the property of some, — a property which 
seems founded in and not accessory to 
their structure ; we may easily believe 
that the concealment of the androconia 
is to prevent the too rapid dissipation 
of the odor, to offer the opportunity for 
its sudden flush, — in other words, to 
[place it under some control. 

The exquisite and varied form of the 
androconia is another matter. They dif- 
fer marvellously from ordinary scales in 
the variety of their form and exquisite 
structure. Ordinary scales seem made on 
a single pattern ; they are minute enough, 
but they are huge as compared with most 
androconia. Why such delicate and ex- 
quisite patterns on such a microscopic 
scale? Who is to see and enjoy them? 
Assuredly not the butterflies themselves ; 

Scent-Scales. 109 

they may profit, indeed, by their function, 
and no doubt natural selection has per- 
fected that to an extraordinary degree, 
well beyond our ken ; but the androconia 
must practically be quite invisible to 
them. Is there not here, then, a beauty 
of form and of structure which is an 
end in itself, of no possible profit to the 

[Readers wishing to look into this subject more fully 
will find it discussed in detail in my " Butterflies of the 
Eastern United States" (see particularly Excursuses 
xvi. xxzi. xl. Ixvii. and Ixx. and plates 43-51), where 
also references will be found to the literature of the 


Insect yision. Does Sight or Smell most 
control the action of Butterflies? 

|N the last chapter we pointed out 
the existence in many male 
butterflies of structures of extra- 
ordinary variety, and considering their 
microscopic size, of remarkable complex- 
ity, which are so hidden from sight that 
they can rarely or never be seen by their 
neighbors, even if we credit the latter 
with exceptional powers of vision. A 
lurking feeling may yet exist in many 
minds that they may, after all, be thus 
endowed; and we therefore depart a 
moment from the general method em- 
ployed in the present work of setting 
forth the life of a single butterfly, to 

Insect yision, iii 

inquire whether it may or may not be 
true that insects, our Milkweed Butterfly 
of cours.e included, have remarkable 
powers of sight, for then we shall be 
better able to interpret many of their 
lines of conduct. 

Vision in insects with compound eyes 
has been a subject of discussion for very 
many years, and the views of naturalists 
regarding it have differed from time to 
time very considerably. The question 
has recently received much new light 
from the anatomical investigations of y 
Patten and others, and the experimental 
researches of Forel and Plateau. The 
compound eyes of butterflies, as of other ' 
insects, are made up externally of a num-/ 
ber of adjoining hexagonal facets, eacU 
separate facet being the exposed portion 
of a crystalline lens which is followed 
beneath by a slender tube containing, 
first, a terminal body, the crystalline cond^ 
or retinidium, — formerly looked upon as\ 
a second refracting medium, but by Patten 

112 The Life of a Butterfly. 

regarded as a retinal body sensitive to 
the light, — and second, of a collection 
of rods. 

The office of this so-called crystalline 
cone is the principal point in dispute. 
The later researches regard it as a recep- 
tacle for the termination of the nervous 
elements, and as performing no office in 
either modifying or destroying the image ; 
while the old view regarded it as having 
similar properties to the crystalline lens 
of our own eye. Now if the later view 
be regarded as correct, which there seems 
every reason to believe, the form and 
nature of this receptacle is such, as 
Plateau points out, that an iniage may 
be formed at any point within its depth; 
but at the same time all the sensitive 
points of the cone in advance of or behind 
an image will be illuminated and will also 
to some degree be excited by the same 
object, so that whatever image is formed 
can in no way be seen as distinct, but 
only as entirely confused, much as hap- 

Insect yision. 113 

pens in the human eye when the image 
is focussed beyond the retina. 

This theoretical view can be perfectly 
well subjected to experiment; and this 
has been done in the most thorough man- 
ner by the Belgian naturalist, Plateau. 
At first his experiments were made almost 
entirely by placing the insect desired to 
be experimented upon at one end of a 
closed compartment at whose other end 
were two distinct openings to the light, 
— one simple and large enough for the 
escape of the insect, the other much larger 
but covered with a trellis or grating, so 
that while the actual superficial area of the 
open spaces might be the same in each 
case, admitting the same quantity of light, 
the trellised opening would appear greater. 
At the same time one could modify at 
will the amount of light which would 
enter either of these two different classes 
of openings. The insects almost invari- 
ably flew to the trellis. Numerous experi- 
ments were made by Plateau upon this 


114 ^*^ ^?/^ ^f ^ Butterfly. 

basis, resulting in his concluding that 
insects with compound eyes did not 
well distinguish between two illuminated 
openings, being sometimes led astray by 
the excess of luminosity, sometimes by 
the apparent excess of surface. In gen- 
eral, he thought they could not dis- 
tinguish the form of objects, or only in 
a vague way. 

Objections were raised that in these 
cases it was not objects, but luminous 
openings, the power of seeing the form 
of which was tested; and also that the 
judgment of the insect was brought into 
service under unnatural conditions, so that 
the experiments proved nothing very 
definite or decisive regarding the actual 
power of vision on its part. Thereupon 
Plateau devised a new method by which 
experiments could be made, obviating all 
these objections, and has carried out 
these experiments even more carefully 
and extensively than the previous, insti- 
tuting, moreover, comparative investiga- 

Insect yision. 115 

tlons with the vision of vertebrates under 
precisely similar circumstances. 

To do this he constructed what he has 
termed a labyrinth, — a table covered with 
a large number of vertical barriers placed 
in concentric series in such positions that 
the creature must take a very circuitous 
course among them to escape. Of course 
only crawling insects could be experi- 
mented on, but the structure of the eyes 
is essentially the same in all. Care was 
taken that the coloration of the surface 
should be of a neutral tint, and the 
vertical barriers were painted of various 
colors, — white, brown, or black ; also that 
the animal should begin its movements 
without excitement, by the quiet lifting 
of a glass cover under which it had been 
placed, near the centre of the labyrinth, 
when it would find itself surrounded 
by walls between which were abundant 

Where the vision was really good, the 
animal would be expected to move in a 

1 1 6 The Life of a Butterfly. 

serpentine course between the obstacles, 
never striking them, usually moving 
toward the opening which was largest 
or nearest. When, however, the power 
of vision was to some extent defective, 
so that the animal seemed to be aware 
of the existence of an obstacle only 
when it had almost reached it, then the 
movements should be made in a series 
of zigzags which would change direction 
somewhat sharply, shortly before the 
barriers were reached. Or if the vision 
were absolutely defective, the creature 
would be likely to find its way only by 
first striking the objects and then moving 
around them. 

The result of his experiments proved 
that vertebrates had complete vision, 
directing their movements with ease 
without striking any of the obstacles, 
moving in the nearest path ; while insects 
acted in all cases as if they had a 
veil befpre their eyes, — their change of 
direction before reaching the barriers 

Insect yision. 


being such as to indicate that it was 
only when they reached the shadow of 
the obstacles before them, when they 
could distinguish some difference in the 
intensity of light, that they turned aside 
to avoid such obstacles. 

The result of these experiments has 
been so uniform and so clear that how- 
ever the actual anatomical structure of 
the eyes of insects may be regarded, 
there can be little doubt that their vision 
is so extremely imperfect that they per- 
ceive sharp images of nothing immobile, 
and therefore do not distinguish the 
precise form of objects, though they can 
readily distinguish objects in motion. 
Indeed, they are particularly keen in this 
sort of vision, so that their sight must 
be best while upon the wing ; for in this 
case it is the same as if they were at 
rest while all the objects about them were 
moving. So too, they can distinguish 
masses of color, but not pattern, except 
in the vaguest way. The comparative 



1 1 8 The Life of a Butterfly. 

experiments revealed an enormous differ- 
ence in the behavior of vertebrates and 
insects under precisely identical circum- 
stances, — the former acting as if they 
possessed human vision, the latter as 
if they could distinguish the form and 
boundaries of objects in a most imperfect 
way, at the best. 

"A flying insect," says Plateau at the con- 
clusion of his various experiments, "has a 
very lively perception of light and shadow, so 
that without distinguishing as we should do all 
the details of its route, it knows how to avoid 
all masses, such as the trunks of trees, bushes, 
rocks, walls, etc., and passes them at a con- 
venieat distance. Caught from any cause in 
a mass of shrubbery or any other group of 
vegetation, it takes advantage, when it wishes 
to pass on, of those passages through which 
the greatest amount of light filters, or as 
, between two equal in this respect, of such as 
\ seems to it to offer the most room. If the 
wind move the leaves, these openings may 
i^scillate, but thanks to its good perception of 

Insect Vision. 119 

movements, the insect can then see them 
better. In flying, the insect moves in undula- 
tions so as to follow the direction of the 
displacements and to traverse the openings 
without striking. 

" When its mode of sustenance necessitates 
a visit to certain flowers, it moves toward them 
either with certainty, in being guided by itJv 
sense of smell only, if its power in this direction 
is well developed, or by chance if its olfactory 
powers are relatively slight. Incapable of dis- 
tinguishing by their forms flowers of the same 
color, it goes directly toward the colored spots 
which to it mean corollas or inflorescence, 
turns, hesitates, and does not decide what to do 
until the distance has become sufficiently slight 
to enable it to determine by the odor whether 
or not it has found what it seeks. 

" The sense of smell only, or this combined' 
with visibility of movements, assures the meet- 
ing of the sexes ; and finally it is the perception 
of movements which warns of the approach of 
an enemy and permits escape in time. 

"This brief statement is sufficient to show 
how an insect with facetted eyes^ though it 


1 20 The Life of a Butterfly. 

only has a confused visual perception of objects 
at rest, frequently acts in a manner to suggest 
to one who does not closely analyze the 
phjenomena that the eyesight of these creatures 
is as distinct as that of the vertebrates." 

It may be added that in his experi- 
ments Plateau found that the family of 
butterflies called Lycaenidae, of which 
our tiny blue butterflies may be taken as 
a type, were disturbed by a moving object 
only when at half the distance at which 
one of the Nymphalidae (like our Milk- 
weed Butterfly) would take alarm. Now, 
if we examine the eyes of these two 
groups we find a singular difference which 
may account for this : each of the eyes of 
the Nymphalidae covers the continuous 
surface, roughly speaking, of half a 
sphere; in the Lycaenidae the posterior 
half of this half-sphere entirely lacks any 
facets; indeed their ocellar globe has 
relatively the smallest visual surface of 
any butterflies ; this fact at once explains 
their tremulous movement before alight- 

Insect yision. 121 

ing on an object; they seem to be 
forever uncertain just where it is best 
for them to settle. 

Soon after the publication of Plateau's 
observations, I was interested in watch- 
ing at leisure the movements of a couple 
of wasps searching for flies along the roof 
of a tent in which I lay upon my back 
in my camp among the Rocky Mountains. 
There were a dozen or twenty flies in the 
tent, which when not in motion were 
alighted on a rope which stretched loosely 
just below the ridgepole. The wasps 
were in incessant motion, and in the 
course of the morning were seen to cap- 
ture only three or four flies, the flies 
usually being able to dodge them when- 
ever an attack upon them was made. I 
was unable to see that a wasp accelerated 
its motion in the least when approaching 
the flies, or directed its flight immediately 
upon them, until within two or three 
inches of its intended victim; and as it 
often passed one by at no greater dis- 

1 22 The Life of a Butterfly. 

tance than this without any attempt at 
capture, the impression was strong that 
the wasp's distinct vision while in flight 
did not exceed this distance. 

But what was most surprising was the 
great number of mistakes made by the 
wasps. Every slight stain or defect in 
the canvas or minute shadow upon it was 
repeatedly attacked by the wasps as if 
they supposed it to be a suitable object 
for food. There seemed to be no power 
on their part of distinguishing between 
a spot of color upon the canvas having 
no elevation whatever and an object or 
body resting upon it. Several times the 
shadow made by a fly alighted upon the 
outside of the tent was pounced upon by 
the wasps on the inside, and such objects, 
mere shadows or stains, were repeatedly 
attacked by the same wasp over and over 
again, often with only half a minute's 
interval or even less than that. I cannot 
now recollect exactly the estimate I made 
at the time (but failed to record) of the 


Insect Vision. 123 

relative number of attacks upon false 
objects to those upon proper victims, but 
I am under the impression that the mis- 
takes were to the correct judgments as 
twenty or thirty to one. These obser- 
vations lasted two or three hours, and 
certainly seem to show that the vision 
of these insects even when in flight is 
exceedingly defective, judged by our own 

Now let us apply these conclusions 
(the imperfect and vague power of vision 
and the keen sense of smell) to two of 
the principal acts in a butterfly's life, 
having to do with the perpetuation of 
its kind, — the meeting of the sexes, and 
the deposition of the eggs for the next 

The presence of scent-producing andro- 
conia is supplemented by other known 
scent-organs in other parts of the body, 
principally in the abdomen, numerous 
instances of which have been collected by 
Frit? Miiller, Haase, and others; indeed 

124 The Life of a Butterfly. 

the literature of the subject is becoming 
somewhat extensive. Now the mere pres- 
ence of scent organs confined to one sex 
is in itself ample evidence that the odors 
are perceptible to the opposite sex, and 
we have in certain specific structures in 
the enlarged antennal club of butterflies 
what are plainly sense-organs supplied 
with nerve endings ; and inasmuch as 
there is no structure found in them which 
could subserve the purpose of hearing, 
or indeed of any other of the senses 
known to us excepting that of smell, it 
is the belief of physiologists that here 
are situated the organs of smell in 

The under surface of the antennae of 
butterflies is invariably naked to a greater 
or less degree ; and more plainly in some 
joints than in others, little dimples can be 
readily seen. It is in these little pits that 
are situated the organs of smell; each 
consists of a sac-like cavity, the opening 
into which is often protected by cuticular 

Insect P^ision. 125 

processes, and at the bottom of which in 
the hypoderm is situated a fusiform body 
with a delicate conical ending extended 
free into the centre of the sac, its other 
extremity being in direct continuation of 
a nervous thread. 

The assembling of male moths around 
a concealed female already alluded to, 
and the strange gathering of the males of 
our Southern butterfly, Apostraphia chari- 
thonia^ around the female chrysalis just 
before and at its eclosion, so graphically 
described in Mr. Edwards's sumptuous 
work on American butterflies, are indubi- 
table witnesses to the importance of the 
sense of smell in effecting the union of 
the sexes. That this sense is endowed 
with a keen discriminating quality will 
hardly be questioned by those familiar 
with the immense abundance of indi- 
viduals of closely allied species in any of 
the warmer parts of the world, and the 
excessive rarity of known hybrids. It is 
difficult for us, with our dull powers, to 

126 7be Life of a Butterfly. 

appreciate it; but granted, it is amply 
sufficient to explain the proper union yf 
the sexes in the heterogeneous multitude 
of butterflies which swarm within the 
tropics ; and when we remember that 
in a very large number of cases it is 
impossible for the trained naturalist to 
discriminate between closely allied but- 
terflies in the field (and often exceedingly 
difficult in the laboratory) one must be 
led to the conclusion that the imperfect 
vision of these creatures can prove in no 
way sufficient for the continued existence 
of the species, but that the sense of smell, 
brought to a high degree of perfection in 
the struggle for existence, alone has the 
power of saving them from extermination, 
by enabling each kind to choose its 
proper mate. 

The same thing appears in the ques- 
tion of food for the young caterpillar just 
hatched; this must be near at hand, or 
it will perish. Yet caterpillars are very 
choice of their diet, some extraordinarily 

Insect yision. 127 

so. That of our Milkweed Butterfly, for 
instance, will eat nothing but plants of 
the genus Asclepias, and occasionally 
Acerates and Apocynum, — one belong- 
ing to the same order, the other its 
next-door neighbor; even in Asclepias 
it has its favorites. 

But there are some butterflies whose 
food in early life is even confined, so far 
as known, to a single species of plant; 
none are indiscriminate feeders, and the 
great majority are restricted to a very 
few sorts. Moreover, closely allied 
butterflies may feed on widely diflferent 
kinds of plants, as for example, our com- 
mon yellow butterfly, Eurymus philodice^ 
which lives on Leguminosae, and Legu- 
minosae alone, and principally on clover ; 
while its near neighbor, E, interior^ hard 
to distinguish from it, has been found to 
die rather than touch clover or a doz^n 
other kinds of Leguminosae, but feeds 
instead on Vaccinium, one of the Eri- 
caceae, botanically far removed. 

128 The Life of a Butterfly. 

How, then, does the parent infallibly* 
discover the plant upon which it should 
lay its eggs? This is an act of instinct, 
one will say. But is this any expla- 
nation? We wish to know how the 
instinct acts. A parent butterfly that in 
its caterpillar life has been nourished upon 
willow, has no means in the winged con- 
dition of tasting the willow to recognize 
it, its organs for obtaining food being 
suited only for liquid nourishment. Nor 
can it be by sight 

It is true that butterflies are attracted 
by flowers through their means of vision. 
Interesting stories are told of their being 
deceived by painted or artificial flowers. 
But in these cases there is no reason to 
suppose that it is anything but the tint in 

* The cases are exceedingly few, may almost be 
counted upon one's fingers, in which the eggs of butter- 
flies are known to have been laid in free nature on 
anything but a plant on which the caterpillar will feed ; 
and in those few cases the proper food-plant was near 
enough for the caterpillar easily to reach it in its wan- 
derings, — within 9. fevr feet, for instance. 


Insect yision. 


mass that attracts them to the coveted 
spot. Pray how differs the green of one 
plant from that of all others ? In the case 
of those which feed upon a considerable 
nuniber of plants they must have all the 
powers a trained botanist has at command 
if it be by the form of the leaves, when 
nearly every leaf they might properly 
choose could be almost exactly dupli- 
cated by another as good as poison to 
them. No ! Anatomy and experiment 
both teach us that butterflies have no 
vision sufficiently clear for any such 
powers of distinction as are required of 
them in selecting special food plants for 
their young, which yet they discover in 
an unerring manner. 

There remains, then, apparently nothing 
but smell. Now we know that many 
plants are odorous quite apart from their 
flowers, and that the leaves and other 
parts of plants, as well as the flowers, are 
furnished abundantly with special struc- 
tures, like nectar glands, glandular hairs, 



The Life of a Butterfly. 

and other glandular devices, from some 
of which odors are exhaled perceptible 
to our dull senses, — perhaps from many 
others, perceptible to keener organs ; and 
if one with this in mind will but watch 
the movements of a mother butterfly seek- 
ing a spot whereon to lay her eggs, he 
will not fail to recognize that many of 
these actions seem particularly in keep- 
ing with the notion that she is at work 
scenting the various plants that bear a 
general resemblance in their aspect to 
the plant which she seeks (many, indeed, 
which have no such general appearance), 
settling or half-settling in a dozen differ- 
ent places in the near vicinity of the 
plant, reaching it by nearer and nearer 
approaches, and finally settling with satis- 
faction at the desired spot. To such an 
observer it will seem tolerably clear that 
it is to the sense of smell that butter- 
flies owe their recognition of botanical 
The consequences of the conclusions at 

Imect yision. 131 

which we have arrived are far-reaching. 
If vision plays such a secondary part in 
the life of insects, then the whole struc- 
ture upon which the theory of sexual 
selection in insects has been based is at 
fault, and it supports the objections to it 
which Wallace has brought on other 
grounds. It shows that the recognition 
of the food plant by the mother, which 
does not and cannot taste it, must be by 
some other sense than that of sight. It 
shows that the very high development 
of scent scales of varied patterns and 
character among male butterflies, indi- 
cating a direct sexual use, can only be 
understood if we regard the greater 
variety and brilliancy of the colors of 
butterflies as contrasted with moths to . 
have no sexual significance whatever, i 
Brilliant masculine colors may possibly 
have arisen in birds through sexual 
selection, but such an origin is impossible • 
in butterflies with their vague vision ; and 
as the males cannot be attractive to their. 

132 The Life of a Butterfly. 

mates by seductive colors, they resort to 
odors, and vie with each other in the pro- 
duction of sweet-smelling garments. It 
becomes clear that the exquisite beauty 
and variety in the butterfly world is not 
recognizable by themselves, and forms no 
element in their lives. 


The Fore Legs of the Male and the Hating of 
the Chrysalis : a Lesson in Classification. 

|ACTS, I once heard Agassiz say 
in one of his lectures, ** are stupid 
things, until they are brought 
under some general law." It has no 
special interest or significance, in itself 
considered, to know that our Milkweed 
Butterfly when a chrysalis is suspended 
by its tail. It is curious, of course ; but it 
has no real meaning in itself alone, — it 
is then a stupid, barren fact. The study 
of the structure or transformations of any 
creature has more than a merely transi- 
tory interest only when comparisons can 
be made with the parts and changes of 
other creatures, and we can ask what are 

134 The Life of a Butterfly. 

the differences between them and what 
the causes thereof. It is of far greater 
interest to compare the morphologically 
identical but physiologically different 
human hand and foot than the fore and 
hind foot of, say, a fox, both morpho- 
logically and physiologically the same. 
So when we come to any repeated struc- 
ture in an animal, and find it repeated in 
a different way, we inquire at once into 
its meaning and are unsatisfied until this 
be discovered. 

Now there is one point of this sort that 
would particularly pique the curiosity of 
an inquirer if he were to study the struc- 
ture of our Milkweed Butterfly; for he 
would soon learn that while the creature, 
like all insects, has three pairs of legs, it 
walks or rests on only two, and keeps 
the front pair folded against the breast, 
the ends hanging down. And if he were 
to examine this pair more closely, he 
would find that not only are all the parts 
abbreviated, but that the joints of the 

A Lesson in Classification. 135 

tarsi are all run together, particularly in 
the male, and that the claws, being use- 
less, are entirely wanting ; in short, the 
whole leg, though flexible, id atrophied, 
and of no actual use at ^ill. 

What is the next step the inquirer 
would be likely to take? Why, naturally, 
to see whether other butterflies were so 
made. Suppose him next, then, to catch 
a Swallow-tail Butterfly, as a larger sort 
easy to examine. W^ell ! here, with slight 
variations in length, all six legs are pre- 
cisely alike, excepting that those in front 
have a little flabellate appendage to the 
tibia which is not found on the other 
legs or on the fore legs of the Milkweed 
Butterfly. Instead of being deficient, 
they are redundant; hypertrophy re- 
places atrophy, and the leg is used like 
the others. If he have the spirit of the 
naturalist, nothing will now satisfy our 
inquirer until he has examined all the 
butterflies he can lay his hands upon, — 
the more so as he will find an extraor- 

136 The Life of a Butterfly. 

dinary diversity among them, and yet 
among similar kinds great similarity. 

It is by just such comparisons as these, 
applied to "every part, — the subdivisions 
of the trunk, the structure of the antennae, 
the eyes, the palpi, the tongue, the wings, 
and the legs, — that we learn the relation- 
ships of butterflies, and group them into 
their various families, subfamilies, tribes, 
and genera. And we have to study as 
well the structure of the insect in its 
earlier stages, — the egg, its form and 
sculpture, the caterpillar, its shape and 
clothing, and the chrysalis with its special 
mode of suspension, its form, and the 
relations of its sheathed limbs. Even 
the habits bear their testimony, and the 
structure of the internal organs as well. 

The proper classification of butterflies 
thus involves not only the carrying in the 
mind an endless array of detailed facts 
drawn from every part of the body of 
the diff*erent creatures in their several 
stages of existence, but also the proper 

A Lesson in Classification. 137 

valuation of the facts, — whether they are 
of considerable importance to the life of 
the animal, whether they may be traced 
through long series, whether they are 
correlated with others which are equally 
or almost equally extensive, whether they 
may be related to a past phase of exist- 
ence now of no concern, and so on. A 
successful naturalist, then, is one who 
with the largest knowledge combines the 
keenest insight into valuations^ and can 
most surely divine the blood relationships 
of the present and the past; for only so 
far as our classifications give us an insight 
into blood relationships do they have any 
value whatever. 

To apply these remarks in more definite 
fashion, let us proceed to the inquiry 
whether the structure of the fore legs 
of the perfect butterfly or the mode of 
suspension of the chrysalis gives us any 
probable clew to relationships among 
these creatures. To do this in the brief- 
est and simplest way it will be convenient 

138 The Life of a Butterfly. 

to premise that butterflies are generally 
regarded as divisible into from four to 
six great families, — the Hesperidae, or 
Skippers; the Papilionidae, or Typical 
Butterflies (divided into two subfamilies, 
the Pierinae, sometimes regarded as a 
distinct "family," and the Papilioninae 
proper); the Lycaenidae, or Gossamer 
Wings (divided into two subfamilies, the 
Lycaeninae proper and the Lemoniinae, 
sometimes, perhaps generally, regarded as 
a separate " family"); and the Nymphali- 
dae, or Brush-footed Butterflies (divided 
into a number of subfamilies, many of 
which have been regarded as " families " 
by different authors). 

The ** family " or ** subfamily " value of 
a group is of relatively little importance 
as compared to determining who are its 
neighbors, and in all the varying cases 
given above there is no question in this 
particular on the part of any one. No 
one would venture to separate by the 
interpolation of another group the Lycae- 

A Lesson in Classification. 139 

ninae from the Lemoniinae on the one 
hand or the Pierinae from the Papilioninae 
on the other. By universal consent they 
must accompany each other, whether they 
are regarded as families or subfamilies. 
There has, however, been a considerable 
difference of opinion regarding the relative 
position of the four great groups among 
themselves. Will the structure of the 
legs throw any light upon this question? 
Let us see. 

In the Hesperidae the fore legs, like 
those of the moths (which form the other 
and lower extreme of the series of Lepi- 
doptera, to which butterflies belong), 
differ in no respect from the other pairs, 
excepting that the hind tibiae are usually 
furnished with a pair of spurs at the 
middle as well as at the tip, and the fore 
tibiae bear near the middle a peculiar 
flabellate appendage, the use of which is 
unknown, but which, morphologically, is 
unquestionably a spur. 

In the subfamily Papilioninae, the mid- 

I40 The Life of a Butterfly. 

die pair of spurs of the hind legs is 
altogether lost, but the fore-tibial appen- 
dages remain, and the fore leg is 
otherwise entirely similar in character 
to the other legs. Next, in the closely 
allied subfamily, Pierinae, the fore-tibial 
appendages disappear, but the fore legs 
still remain identically like the other 

As soon, however, as we have reached 
the Lycaenidae, we notice signs of an 
abortion of the fore legs, but only in 
one sex, the male. In the subfamily 
Lycaeninae, while the fore leg of the 
female does not differ from the other 
legs, that of the male begins to lose a 
part of its armature and to become abbre- 
viated : the tarsal spurs are denuded of 
scales, and both the tibial and tarsal 
spines are diminished in number; the 
paronychia and pads at the tip are 
invariably absent ; and the claws are rep- 
resented by an apical spine or spines 
differing from the other spines at most in 

A Lesson in Classification. 141 

size. In the subfamily Lemoniinae the 
change has become much greater; for 
.with scarcely an exception, the fore leg of 
the male has become very much smaller 
than in the female, and while each part is 
reduced in size, the tarsus is represented 
by a diminished number of joints, totally 
devoid, as is also the tibia, of any arma- 
ture whatever, but clothed abundantly 
with long scales and hairs. There is 
here also sometimes a faint indication of 
change in the female, the spines of the 
tarsus being less abundant than on the 
other legs. 

In the Nymphalidae, the change affects 
both sexes; not, however, in the lowest 
subfamily, the Libytheinae, which, on 
this account, many authors who have 
given special attention to the structure 
of the legs have classed with the Lemo- 
niinae. But in all other Nymphalidae, 
as in our Milkweed Butterfly, we have for 
the first time both sexes fully represented 
in the atrophy of the fore legs, and the 

142 The Life of a Butterfly. 

abortion is also carried to a far greater 
extent. They are also frequently fur- 
nished, especially in the male sex, witl\ 
a spreading brush of long hairs, which 
gives them a peculiar lappet-like appear- 
ance, on account of which they have been 
called Brush-footed Butterflies. They are 
quite useless, and in some are reduced 
to the extremest degree. There is in 
butterflies no other structural feature of so 
great functional importance which differs 
so greatly in the differefit families ^ jitfttT^ 
fo ll o fvs 'US^-k€9^€.ji ^rogres siue course. 

Changing our point of view, let us next 
consider the different ways in which 
chrysalids of butterflies are suspended 
or cared for. It is well known that as a 
general rule moths undergo their trans- 
formations to chrysalis within a cocoon, 
spun by the caterpillar, or in a cell 
moulded beneath the surface of the 
ground. The same is true of the lowest 
family of butterflies, the Hesperidae, 
which usually make such a cocoon within 


A Lesson in Classification. 143 

a rolled-up leaf or cluster of leaves, and 
hence had given them by Boisduval the 
term Involuti, or enrolled. It w<is not 
noted by him, nor has it been, as far as 
we are aware, by any author, though 
figured by many, that within this cocoon 
they generally spin a pair of shrouds, 
into the middle of one of which they 
plunge their cremaster, while by the 
other they support the middle of the 
body. \ 

Now, remove this outer cocoon and 
leave the shrouds, and one has, with only 
such changes as are absolutely required 
by the lack of the encircling cocoon, the 
character of the support of the chrysalis 
of the Papilionidae ; namely, a button of 
silk attached to the object from which the 
chrysalis hangs, and a loose girt around 
the middle of the body. In the Lycae- 
nidae, we pass simply to a still closer 
attachment of these fastenings, so that 
the rounded chrysalis appears almost 
glued to the surface to which it is 

144 The Life of a Butterfly* 

attached; and these two families, the 
Lycaenidae and the Papilionidae, were 
classed by Boisduval under his Succincti, 
or girt. 

In the Nymphalidae, by the loss of 
the median girt, the chrysalis hangs sus- 
pended by its hinder end, and forms the 
group termed by Boisduval Suspensi or 
Penduli, — that is, hung, — which he and 
his followers interpose between the Invo- 
luti and the Succincti. Yet we have here 
a regular progression from the cocoon of 
j the moths to the almost total absence 
i of the use of any silk for the quiescent 
I period of life. The few exceptions to 
this rule seem to be entirely explanable 
as instances of reversion. Thus the only 
case among the higher butterflies where 
a cocoon, properly speaking, is made, is 
in the subfamilies most closely allied to 
the Hesperidae, among the groups of 
Parnassini and Anthocharini,* and again 

* Bar asserts that the same is true in some South 
American Lemoniinae 

A Lesson in Classification. 145 

in exceedingly feeble instances, where the 
necessities appear to be overwhelmingly 
great, among some of the Nymphalidae, 
which have lost even the last remnant of 
the cocoon of moths, — namely, in some 
of the Satyrinae, which lack cremastral 
hooks and undergo their transformations 
ordinarily in the rudest form of a cell 
which they can construct at the surface 
of the ground, by the mere movements 
of the body and the spinning of one or 
two threads of silk. 

Moreover, note this: an additional 
feature appears in the structure of the 
chrysalis of a large number of the Nym- 
phalidae, which would seem to indicate 
that they inherit the mark of the ''suc- 
cinct " condition of their ancestors, in the 
straight ventral surface of the entire 
chrysalis, — a feature absolutely without 
value in its present suspended condition, • 
but full of meaning, since it is one 
necessarily common to all the close- | 

bound members of the Succincti, the 




146 The Life of a Butterfly. 

Lycaenidae. That is to say, the straight 
ventral surface of many hanging Nym- 
I phalidae indicates that this group has 
! passed through and come out of a ''suc- 
cinct " mode of suspension. 

Now it will be observed that these 
two series, drawn from such independent, 
j important, and different sources as the 
development or atrophy of the fore legs 
of the butterfly and the mode of sus- 
pension of the chrysalis, are entirely 
• parallel. Indeed, taken together they 
indicate, with a certainty somewhat rare 
. in the study of animals so nearly allied, 
the general interrelationship of the fami- 
lies concerned, which a study of other 
details of their structure only the more 
ptrongly confirms, — the Papilionidae, for 
^xample, presenting very many more 
points of contact with the Hesperidae 
than can be shown to exist between 
the Nymphalidae and the Hesperidae. 

Each of these families contains groups 
of lesser extent founded on structural 

A Lesson in Classification. 147 

or developmental characteristics of lesser 
value, which it is the aim of the syste- 
matic naturalist to set forth in terms 
which shall be, as nearly as possible, a 
transcript of the teachings of Nature her- 
self. Just so far as he seeks to make it 
his own system, will he fail; just so far 
as he strives to have Nature reveal herself, 
will he succeed. He must not regard 
popular opinion, but seek his sup- 
port solely from Nature. The investigator 
in this field must be modest, patient, 


IVbat is its Proper Name ? A Brief Chapter 
on Nomenclature as used by Naturalists. 

|UCH outcry is made against the 
terminology of natural history. 
But if any one can point out 
a more sensible method than that be- 
queathed to us by Linn6 and his followers, 
none will be more ready to welcome it 
than the naturalists. In this, as in every- 
thing else, the most serviceable method 
will obtain the most service. Indeed, one 
sometimes fancies that the critics forget 
what names are for. They merely stand 
for things, and convenience is their only 
hope of life. They must be brief at any 
rate, whether they have any meaning in 
themselves or not ; and they must follow 
certain rules, or we shall stand in such a 
wilderness that no one can find his way. 

IVbat is its Proper Name? 149 

and the very object for which the names 
are meant will be obscured or lost. 

We have seen that there are various 
groups of butterflies of greater or less 
value, and that each contains other groups, 
until we reach the species and variety. 
Varieties, indeed, were not much consid- 
ered in Linne's time, and it is only 
since Darwin's day that they have gained 
much significance. As the outcome of 
the disputes and arguments about names, 
men have pretty generally agreed to give 
to each different kind of animal a double 
name, — the first indicative of the ultimate 
structural group, or genus, to which it 
belongs; the second a specific name, 
agreeing in gender with the former, which 
has or is supposed to have a Latin form ; 
to which has sometimes been added in 
later times, when needed, a varietal name. 
To all higher groups single names of a 
Latin plural form are given ; and attempts 
have been made, with partial success, to 
have each group of the same category 

I so The Life of a Butterfly. 

bear a similar termination, families to end 
in -idae, subfamilies in -inae, etc. 

Our Milkweed Butterfly, for instance 
(which requires no varietal name), is 
Anosia plexippus^ and it belongs to the 
subfamily Euploeinae (named from one 
of its principal genera, Euploea) and the 
family Nymphalidae (named after one 
of its oldest genera, Nymphalis). As a 
member of the Nymphalidae it shares 
with the others of its family a certain 
number of characteristics which are not 
found combined, and rarely found at all, 
in any member of the other families. As 
one of the Euploeinae it has certain pecu- 
liarities in common with other genera of 
the same subfamily, not found combined, 
generally not found at all, in the other 
subfamilies of Nymphalidae. And as a 
member of the genus Anosia it has cer- 
tain structural characteristics in every, or 
nearly every, stage of life which separate 
it from the other genera of Euploeinae. 

It bears within itself, then, characters 

What is its Proper Name? 15 r 

which belong distinctively to family, sub- 
family, genus, and species, — and it is 
the province of the naturalist to discrimi- 
nate these, — and the terminology of the 
nomenclature is necessary to speak con- 
cisely about them and discuss their 
relationships. Without such a makeshift 
and tool small progress would be possible/ 
Imagine mechanics without names for 
their tools, engineers without a nomen- 
clature for the parts of their machines, 
and you will feebly fancy the naturalist 
without his terminology. 

I have said our butterfly's name was 
Aftosia plexippus. Yet if one were to look 
in the last catalogue of American butter- 
flies, he would not And this name, but in 
the place where it should stand, the words 
Danais archippus. This is certainly per- 
plexing to a beginner ; and the perplexity 
is unavoidable as long as men will not 
think alike and act alike. A name once 
rooted by usage for a few years only, even 
if it can unquestionably be shown that 

152 The Life of a Butterfly. 

such usage is in contempt of accepted 
rules, may have a stronger chance of life, 
such is the natural conservatism of man- 
kind, than one clearly correct. Especially 
is this the case where the mistake has 
been made in some important work by 
an "authority," and the error corrected 
by some unknown but patient worker 
in a less conspicuous volume. In this 
way the name is apt to vary in different 

Now, both names, archippus and plex- 
ippus, have been employed and in 
** usage " from very early times, but it 
has been shown by several naturalists in 
different parts of the world that the 
use of the specific name archippus per- 
petuates an error; and while in other 
countries plexippus is now commonly 
employed, in America, thanks to most 
of our catalogue-makers, archippus still 
often retains its usurped place, probably 
because Boisduval and LeConte used it 
half a century ago. In many cases the 

IVbat is its Proper Name? 153 

question is one of priority of usage, pure 
and simple, and then the older name in 
time gains place, but often only after a 
struggle which is sometimes ludicrous; 
proved priority of baptism is the only 
safe guide, the only chance for real 

As to the differing generic name, that 
is on another basis. Naturalists are not 
agreed and probably never will agree 
about the precise limits of "genera," 
some dividing a given collection of 
species into several genera, some regard- 
ing them as one or two only. Now the 
old genus Danais, as looked at by those 
who use this name for our butterfly, 
comprises a very large number of very 
diverse forms, which the latest students 
of these insects have shown should be 
segregated into a number of groups ; and 
Anosia is the one of these smaller groups 
into which our species fall& 

The use of the generic name, then, 
indicates to some extent the views of the 

1 54 The Life of a Butterfly. 

person employing one or the other term. 
Certainly the more closely we study but- 
terflies (which in the past have been 
studied largely upon superficial aspects 
and by an examination of the perfect 
insect alone) the more shall we be 
inclined to look with favor on structural 
groups of lesser extent, as enabling us, 
first, to formulate statements regarding 
their distribution and relationships which 
will throw new light on many dark spots 
in science ; and second, to correlate their 
differences with those of other groups of 
insects where corresponding minor groups 
are accepted, because the structure of 
these latter insects is not concealed by 
a coating of scales, and their study not 
beset with so many practical difficulties. 

There is still a further reason for 
such a preference. With the beginning 
of systematic zoology, all butterflies were 
grouped in a single genus, Papilio ; study 
had then progressed only so far as to 
seize upon the most salient and obvious 


IVbat is its Proper Name? 155 

points in their structure. As the study 
became deeper and more searching, and 
new forms of very diverse character 
swelled by degrees and at last immensely 
the Dumber of species (even in the last 
edition of his Systema Naturae, a cen- 
tury and a quarter ago, Linnd recognized 
but . about three hundred kinds, while 
now we know at least ten thousand), it 
became necessary to subdivide them into 
a greater and greater number of groups, 
subordinate to one another, and families, 
subfamilies, and tribes were introduced to 
distinguish and class them. The "genus" 
has been more and more restricted with 
the growth of our knowledge, and the 
tendency has all along been to have 
it represent the structural group of nar- 
rowest limitations, while the study of 
the structure of butterflies in all their 
stages has constantly narrowed these 

To object, then, to the employment 
of a "generic" term for the narrowest 

1 56 The Life of a Butterfly. 

groups, when they can be shown to have 
a real foundation, is practically to put 
a check upon the study of their struc- 
ture, which it is the very first business 
of the systematic zoologist to encourage 
and indeed to insist upon. No point is 
so minute as not to merit investigation 
and fair consideration. The researches 
of Darwin surely carry this lesson. 


Some Points not touched upon, and some 
Things we do not yet sufficiently know. — 
A Suggestion for Future Study. 

LTHOUGH in the preceding 
chapters we have given a tolera- 
bly full history of our Milkweed 
Butterfly, and have by this means illus- 
trated in a few instances the structure and 
transformations of other butterflies, there 
are still many points about Anosia plexip- 
pus which have not even been alluded to, 
while our references to others have been 
so meagre that whole classes of phenom- 
ena, some of the highest interest, have 
been left untouched. 

Thus, to confine ourselves for the mo- 
ment to our principal subject, not a word 
has been said either about the growth of 

iS8 The Life of a Butterfly. 

the creature within the egg or about the 
internal structure of the caterpillar, chry- 
salis, and butterfly, — by what processes 
both the internal and the external changes 
are brought about, and in what way the 
new organs, such as the wings of the 
perfect insect, originate, present as they 
are within the body of the caterpillar 
from its earliest life. These topics are 
full of interest both in themselves and in 
the further comparisons with the same 
processes in other butterflies or in still 
other allied creatures. Our present know- 
ledge upon these subjects, however, is 
more limited than that of the topics 
already discussed, and they will not yet so 
readily lend themselves to popular inter- 
est ; and therefore, though it renders our 
little book less complete and symmetrical, 
they are not touched upon at all. 

There is, however, one other topic 
which, having been somewhat widely 
studied, especially in this country, and 
^ot yet more than mentioned here, may 

A Suggestion for Future Study. 1 59 

be briefly stated. I refer to the remark- 
able differences between the earliest and 
latest stages of one and the same cat- 
erpillar. This is less marked in our 
Milkweed Butterfly than in most of our 
butterflies, especially than is common 
among other members of the same family, 
which when adult have bodies and even 
sometimes heads bristly with compound 
spines, and altogether lack such a formi- 
dable appearance in their tender youth. 

The full-grown caterpillar of our Milk- 
weed Butterfly is, as we have seen, a 
gayly striped yellow, black, and green, 
naked or nearly naked worm four or five 
centimetres long, with a black-banded yel- 
low head and two pairs of black flexible 
filaments on the body. When it first 
emerges from the egg, however, it is as 
a pale green cylindrical worm, about 
three millimetres long, with a black head, 
and on its body, scarcely to be seen with- 
out a microscope, are several rows of 
minute papillae, one papilla to a segment 

i6o The Life of a Butterfly. 

in each row, each surmounted by a short 
simple hair about half as long as one of 
the segments. Careful examination will 
also show on each side of the second 
thoracic and eighth abdominal segments 
a somewhat similar but larger and hair- 
less papilla. These last persist through 
life, and as we have seen, grow to more 
importance as filaments; all the others 
disappear completely with the first change 

\ of skin. 

\ . What the meaning may be of this 

; infantile clothing, which in one form or 

/ another is present in the earliest stages 
of all butterfly caterpillars, and is alto- 
gether lost in the subsequent growth, 
usually with the first change of skin and 
completely, but which sometimes per- 
sists through one or more subsequent 
changes, more or less modified, is not 
perfectly clear. In a large number these 
hairs, more or less specialized, are plainly 
the outlets of glands lying at their base, 
secreting fluids which often may be seen 

A Suggestion jor Future Study. i6i 

as droplets at the tips of the hairs; and 
it is possible that in these cases the 
glandular secretion serves as a protec- 
tion to the little creature through its 
odor or offensive taste. 

But this is not the case with all, of 
which our Milkweed caterpillar is an 
instance; and it is altogether probable, 
from the universality of this form of 
clothing and its general simplicity, that 
it has a phyletic significance yet to be 
discovered, — an indication of the nature of 
the clothing of the primitive caterpillar of 
all butterflies, or better, all lepidopterous 
insects, and that the glandular structure 
of some is a secondary feature brought 
about through natural selection. Here is 
a highly interesting and important chapter 
in the phylogeny of insects which will 
well repay the conscientious student. 

Let us now turn for a brief moment to 
some of the phenomena witnessed in 
other butterflies, but which cannot be 
illustrated from the butterfly we have 

1 62 The Life of a Butterfly. 

chosen for special consideration. We 
will mention but one among many. 

Among the subjects of general philo- 
sophical interest which the study of 
animals during the Darwinian epoch has 
brought to notice, few have excited more 
attention and interest than the existence 
in a vast number of animals of two or 
more distinct forms in the same species. 
That this is very commonly true of the 
two sexes goes without saying; but 
besides this it often happens that one 
sex may appear under two distinct guises, 
or that alternate broods of the same 
animals may differ so much from each 
other as in many cases to deceive the 
most acute naturalist into the very reason- 
able belief that they are distinct species. 

Much attention has been given to this 
subject among the butterflies, and we 
have in our native species a consider- 
able number of instances in illustration. 
Indeed a large proportion of our but- 
terflies show, in some peculiarities of 

A Suggestion far Future Study. 163 

the scales of the male sex and their 
arrangement into special patches, a ready 
distinction from the opposite sex. There 
are also a very large number which differ 
from the opposite sex in the general 
color or pattern of the upper or lower 
surface of the wings. Curiously enough, 
when we consider how very generally 
the under surface of the hind wing is 
variegated in butterflies, we rarely find 
in this place any distinction between the 
sexes. It is largely confined, at any rate 
with the butterflies of the temperate zone, 
to the massive coloring of the upper 
surface; and here, whenever one of the 
sexes departs from the typical coloring 
of the group to which it belongs, in 
order to assume a livery distinct from its 
mate, it is almost always the female, at 
least among our own butterflies, which 
is thus distinguished. 

But besides that form of dimorphism 
which simply intensifies the distinctions 
between the sexes, we have in some cases 

164 The Life of a Butterfly. 

a double dimorphism, so to speak, which 
not only distinguishes one sex from the 
other, but divides the members of one 
of the sexes into two distinct groups, 
one of which more nearly resembles the 
opposite sex, while the other may depart 
widely from it. There are cases, such 
as our common yellow butterfly, familiar 
to every out-door entomologist, wherein 
the female, instead of being of nearly 
the same color as the male, with some 
distinctions in the marginal bands, is 
of so very pallid a hue as to strike 
the observer at once. The contrary is 
true as regards the female of the Tiger 
Swallow-tail, Jasoniades glaucus, and the 
male of the Spring Azure, Cyaniris 
pseudargioluSy in which, in certain parts 
of the country, a dark form of the sex, 
with nearly uniform brown upper surface, 
is to be found. 

But dimorphism by no means stops 
here, for we have in some of our other 
butterCt^s quite as striking or even more 

A Suggestion for Future Study. 165 

striking peculiarities. Take for instance 
the case of one of our Angle-wings, 
Polygonia interrogationis. Here is an 
insect where there are two very distinct 
forms in each sex, and in each of which 
the sexes are readily distinguished by 
the coloration of the wings; they differ 
in the brightness and variegation of the 
lower surface of both wings and the ob- 
scurity of the upper surface of the hind 
pair; that is to say, there are four sets 
of individuals, which may be separated 
quite as readily as most closely allied 
butterflies, and more so than a great 
many acknowleged species of the best- 
studied faunas. Nor is this by any means 
the whole statement of the case; these 
two types, bred from eggs laid by 
the same parent, differ not only in the 
markings of the wings, but also in their 
form and in the structure of the male 
clasping organs; in fact, we have two 
sets, permanently distinct from each other, 
and to which we cannot apply the name 

1 66 The Life of a Butterfly. 

of species only because we know them 
to have the same parent. 

Now butterflies seek their own kind 
for mating, and nothing more is needed 
to establish these forms as good species 
than that each should persistently seek 
its own kind. Indeed, one can hardly 
help surmising that they already do so 
to a considerable extent, and that this is 
an instance of an almost formed species, 
beyond which it is almost impossible to 
go without becoming one. Between this 
condition and that of species in which 
the sexes do not differ and there is 
very little variation, there is almost every 
grade of difference, so that we may fairly 
imagine that we know one means by 
which species are originated. Here, per- 
haps, if anywhere among butterflies, we 
ought to suspect that physiological selec- 
tion, the province of which is so well 
insisted upon by Romanes, is beginning 
to play its part in the formation or rather 
the differentiation of species; since be- 

A Suggestion for Future Study. 167 

sides the colorational marks which may 
enable the sexes to choose their mates 
with discrimination, we have the first 
steps toward those changes in the organs 
ancillary to generation which everywhere 
mark absolutely distinct forms, and are 
safeguards against admixture* 

More striking and perhaps more con- 
fusing than these examples are those 
where the dimorphism is seasonal; that 
is, where the butterflies of the first brood 
differ, and sometimes to an extraordinary 
extent, from those of succeeding broods 
the same season; or even where the 
earliest appearing members of a spring 
brood may be separated by coloring, 
pattern, or form of wings from the later 
emerging individuals of the same brood. 

Perhaps the most striking instance that 
we have is in the often quoted case of the 
Zebra Swallow-tail, Iphiclides ajax^ whose 
changes have been so thoroughly worked 
out by Mr. W. H. Edwards. Here each 
form appears at a different season of the 

1 68 The Life of a Butterfly. 

year; marcellus is the early spring type, 
telamonides the late spring, and ajax the 
summer and autumn type. Nearly all 
the butterflies which, in West Virginia, 
emerge from the chrysalis before the 
middle of April, are marcellus; between 


that and the end of May, telamonides; 
after this, ajax. The first two, however 
*do not represent distinct broods, for 
telamonides is not the direct conseasonal 
produce of marcellus, but both are made 
up of butterflies which have wintered as 
chrysalids, — those which disclose their 
inmates earliest producing marcellus, the 
others telamonides; while all butterflies 
produced from eggs of the same season — 
and there are several successive broods 
— belong to ajax. These forms differ in 
the length of the long tails upon the hind 
wings, in the clothing of the front of the 
head, in the extent of the blood-red 
spots upon the hind wings, and in other 
markings, and before their relation was 
known were regarded by all naturalists as 
distinct species. 

A Suggestion for Future Study. 169 

Geographical variation of course occurs 
in butterflies, as in other animals, but 
when this is combined at once with 
seasonal dimorphism, sexual dimorphism, 
and ordinary simple dimorphism, one 
becomes almost hopelessly involved in 
trying to disentangle the threads. One 
such instance is found in our Spring 
Azure, Cyaniris pseudargiolus. 

This species, in which the males and 
females differ considerably in the mark- 
ings of the upper surface, is spread over 
almost the entire North American con- 
tinent. In the extreme North, from 
Labrador to Alaska, it is single-brooded, 
but appears in two forms, lucia and vio- 
lacea, differing largely in the heaviness 
of the markings of the under surface. 
Whether one form flies before the other 
does not appear from any observations 
on the spot, as these are too meagre ; but 
there is certainly nothing to show that 
there is any difference in this respect from 
what we find farther south. To examine 

1 70 The Life of a Butterfly. 

this we must confine our attention to the 
eastern half of the continent. Not far' 
from latitude 45° north, two new phe- 
nomena appear. The butterfly becomes 
double-brooded and trimorphic; and the 
third form, with still lighter markings, of 
which the second brood is exclusively 
composed, appears also as a member of 
the first brood, — the three forms succeed- 
ing each other at least within a month, in 
the order of the heaviness of the dark 
markings of the under surface; namely, 
lucia, violacea, neglecta. Confining our 
attention for the present to the first brood, 
observations would seem to show that in 
the northern part of the belt of its 
trimorphism, the form neglecta is com- 
paratively rare, but that in proceeding 
farther and farther south it becomes pro- 
portionally more and more numerous, 
until, as about Albany, N. Y., it has alto- 
gether usurped in numerical importance 
the place formerly occupied by lucia, 
which entirely disappears at about the 

A Suggestion for Future Study. 1 7 r 

latitude of 41°, except (probably) in 
mountainous districts. At the same time 
the second brood, although apparently 
not more the product of neglecta than of 
violacea, becomes more abundant 

We now reach another belt of country, 
in which we, find the butterfly again 
dimorphic in the first generation, — vio- 
lacea and neglecta, in the order of their 
appearance and the summer generation 
as before. But we have not far to pass, 
say to 38° or 39® north, before we reach 
a new condition, in which the first form 
of the first generation becomes sexually 
dimorphic, — the males appearing under 
two guises, one blue above, the normal 
violacea; the other dark brown, vio- 
lacea-nigra ; and this apparently continues 
as the condition of things as far toward 
the Gulf as the species extends. There 
can be little doubt that this succession of 
changes in passing from north southward 
is modified and interfered with to a con- 
siderable extent by the AUeghanies, and 

1 72 The Life of a Butterfly. 

that on their flanks, in very near vicinity, 
we may find at least some examples of 
all these forms. 

In the extreme West, on the Pacific 
slope, we have a new form, piasus, most 
resembling neglccta, which so far as 
observations have gone appears to be sin- 
gle-brooded in the North, double-brooded 
in the South, and to show no difference 
between the broods, — as sharp a contrast 
as could well be found to the character 
of the species elsewhere ; and it is the 
more strange since in Arizona (though 
it should be noted, among the mountains) 
an ashen-tinted form of violacea appears, 
to which Edwards has given the varietal 
name cinerea. The form piasus occurs 
as far north as Central California. What 
is found immediately to the north of that 
is not well known. At Vancouver, how- 
ever, lucia and violacea are met with, and 
violacea at least in Oregon ; and it would 
seem as if in the intervening area not 
only lucia but also violacea must disap- 

A Suggestion for Future Study. 173 

pear, and leave only the more weakly 
marked Pacific representative of neglecta 
as the remnant of the polymorphism of 
the first brood, and which does not 
become digoneutic until left in possession 
of the field. 

Enough has been said, even in the few 
instances given, to show that we find 
among butterflies topics enough of inter- 
est to any one. Yet it should be pointed 
out that it is only within recent years that 
these varying phases of life and form 
have begun to be studied, and that new 
problems arise with every increase of 
knowledge, with every forward step in 
investigation, so that no one may com- 
plain that the ground is too trodden, or 
that new elements of interest may not 
arise by honest search. Surely the know- 
ledge yet to be gained from the study 
of the life histories of butterflies will 
prove far beyond anything we are yet 
acquainted with, just as the problems 
discussed the past twenty-five years are 

174 ^^ ^if^ 9f ^ Butter Jly. 

of far wider interest than those which 
went before. 

Even in the case of Anosia plexippus^ no 
one can say that further study is not 
required, for although this interesting but- 
terfly is one of our best-known species, 
there are several points in dispute regard- 
ing it, and many features in its history 
which need further investigation. The 
movements of the butterfly in the spring 
and in the autumn will require systematic 
and concerted observation over a wide 
extent of territory before their satisfactory 
solution can be expected. Where swarms 
and bevies occur, they should be carefully 
observed from day to day and hour to 
hour, to study the movements and intent 
of the throng. 

The whole question of the regular or 
irregular migration of butterflies can be 
studied better with this species than with 
any other in the world, because there is 
none so subject to congregational move- 
ments which occurs where so many 

A Stligestion for Future Study. 175 

intelligent observers are stationed. If, as 
I think I have shown it to be probable, 
there is over the entire extent of the 
country inhabited by it, at least east of 
•the Rocky Mountains and north of the 
Gulf States, a periodic movement of the 
butterfly, to the south in the season which 
corresponds to the end of September in 
New England, and to the north in the 
time of the first (and in the middle belt, 
of the second) season of egg-laying, then 
observers ought to note at these periods 
the general direction of movement — not 
over a few feet or rods, but as far as the 
eye can follow them — of as many speci- 
mens as possible, tabulate them, and 
publish the results. By this means I 
believe a periodic movement could finally 
be as well established as the annual 


migrations of birds; to this work every 
one can contribute who knows the butter- 
fly by sight. 

Then we need many more careful obser- 
vations on the immunity supposed to be 

176 The Life of a Butterfly. 

enjoyed by this butterfly in its various 
stages, — an immunity certainly not per- 
fect^ and the exact nature and extent 
of which will reward only patient and 
conscientious field work. It would be 
interesting to know the relative willing- 
ness with which insectivorous birds would 
devour the caterpillar and that of the 
Black Swallow-tail, Papilio polyxmes^ 
which feeds on parsley, etc., and bears 
some resemblance to it. The life history, 
and particularly the number of broods 
in a season, should be worked out inde- 
pendently in many places, and for several 
seasons in each, to determine questions 
in which writers are at variance. For this 
the condition and abundance of the but- 
terfly should be observed from week to 
week, and with it the relative numbers of 
caterpillars in each stage, tabulating all 
the facts that can be obtained, including 
observations of the ovaries of such 
females as are captured. 
The following would seem to be an 


A Suggestion for Future Study. 177 

interesting and valuable experiment for 
some one having access to a greenhouse 
empty in summer to try: place together 
males and females reared from July ♦cat- 
erpillars in the northern half of New 
England, without other admixturey iii 
such a greenhouse, covering the open 
windows with netting to prevent escape, 
and placing an abundance of Asclepiads 
in bloom and in young shoots within. If 
the butterflies will breed in confinement, 
then the females should lay eggs, if, as 
some believe, there are in this district two 
broods of butterflies from July on; they 
should not lay eggs if, as I believe, there 
is but a single generation. Coupled with 
this there should be similar experiments 
farther south, where there is more than 
one brood, to see whether they will breed 
at all in such confined quarters. 

There are still further inquiries that 
should be made, if we wish to pursue the 
study of this insect beyond our own 
borders ; for what has been written above 


1/8 The Life of a Butterfly. 

regarding its distribution in recent years 
opens the question as to the progress it 
is making in overspreading the globe, and 
whai effect its introduction may have 
upon the other butterfly inhabitants of 
the regions it invades. In New England 
our newly introduced cabbage pest, Pieris 
rapae, has practically exterminated our 
native Pieris oleracea, except in wild 
regions, apparently by getting a few days 
start of it in the season and monopolizing 
the best feeding-grounds. Then, as the 
Milkweed Butterfly has been shown to 
vary considerably when individuals from 
North and South America and the West 
Indies are compared, the origin of the 
Pacific hordes may perhaps be traced by 
seeing to what type they correspond. 
The variation itself has been in no way 
properly studied, and it remains to inquire 
whether the wanderers in the Pacific are 
going to show any departure from the 

In considering the exotic distribution 


A Suggestion for Future Study. 179 

of the Milkweed Butterfly, it should, 
moreover, not be forgotten that in reach- 
ing the Old World it may be said to 
have reached its own, for Anosia does 
not belong to the exclusively New World 
type of Euploeinae, Ithomyini, but is 
one of the exceedingly few New World 
genera of the otherwise Old World type, 
Limnaini. The work, then, that still re- 
mains to be done on this one insect 
might well engage a lifetime, and we 
are the first to show how insufficient a 
presentation of the subject the present 
volume affords! 


(all the plates illustrate anosia plexippus.) 

Plate L 
The Male Butterfly; natural size. 

Plate IL 

Figs. 1-5. Front view of the head of the cater- 
pillar, at each of its five stages; the line 
beneath each indicates the width'. 

Fig. 6. Caterpillar, last stage ; natural size. 

Fig. 7. Egg ; enlarged about 17 diameters. 

Fig. 8. Caterpillar, first stage ; enlarged about 
14 diameters. 

Fig. 9. Longitudinal section through the female 
butterfly to show the internal anatomy: — 
/, tongue; p, palpus; a, antenna; pr, pro- 
thorax; mes, mesothorax; met, metathorax; 
ps, pharyngeal sac; b, brain; sog, suboeso- 
phageal ganglion ; 1-2, blended first and second 
ganglia of the caterpillar; 3-4, blended third 
and fourth of same ; /, /, /, the three legs ; ac, 
aortal chamber; dv, dorsal vessel; oe, oeso- 
phagus; res, reservoir for air or food; j/, 
stomach ; mv, malpighian vessels ; i, intestine ; 

Explanation of the Plates. i8i 

c, colon ; r, rectum ; cp^ copulatory pouch ; o, 
oviduct; tfg', accessory glands ; j;^, spermotheca ; 
ov^ ovaries (not fully developed); nc^ nervous 
cord. Enlarged 3 diameters. 

Plate III. 

Fig. I. Side view of the appendages of the butter- 
fly a little enlarged, with some separate parts 
further enlarged : — /, palpus ; /*, fore tibia and 
tarsus, male and female ; /*, tip of fore tarsus 
of female ; mf^ fti!\ side and dorsal view of last 
joint of middle tarsus of male. 

Fig. 2. Side view of the denuded extremity of the 
abdomen of the male butterfly, showing the 
pencil of extensile hairs in place. Enlarged. 

Fig. 3. Greatly enlarged view of part of dorsal 
surface of hind wing of the male butterfly, 
showing the distribution of the scales on and 
about the lowest median nervule and the 
adjoining pouch. 

Fig. 4. Cross section through the same, showing 
the nervule and the pouch, the latter the 

Plate IV. 

Figs. 1-6. Scales from the hind wing of the male 
butterfly : 1-3, from the edge of the pouch ; 
4, from the vein next the pouch ; l-dy from the 
interior floor of the pouch. Greatly enlarged. 

Fig. 7. Rear view of chrysalis ; natural size. 

Fig. 8. Longitudinal section of the head to show 
the pharyngeal sac : — wr, left maxilla (the 
right removed) ; mfl^ floor of mouth cavity or 


-» --^ 

1 82 Explanation of the Plates. 

pharyngeal sac ; o^, oesophagus ; ov^ oral valve ; 
sdj salivary duct ; dm^ fm^ dorsal and frontal 
muscles which open the sac. Above the sac 
are seen the cut ends of the transversely encir- 
cling muscles which close the sac. Enlarged 
about 20 diameters. 

Fig. 9. Side view of chrysalis ; natural size. 

Fig. 10. Cross section of the spiral tongue, the 
anterior portion uppermost, to show the mode 
in which the two halves unite to form a central 
canal through which the fluid food ascends f — 
c^ central canal; /r, trachea; », nerve; tn^ m\ 
muscles of one side. Enlarged about 125 

[Plate I. b from the original by C. V. liley. Plate II. 
fig. 9, plate III. fig. 2, and plate IV. figs. 8 and 10 are from 
the originals by Edward Burgess.] 



Agassiz, U q 

Androooiua, 10 

Aoosia plexlpi 
veed Butter 
AntiiAea, ic 
^pocynum ai 

A*, "7. 
Atgrmtts at 






H\ii C 





Aceratei u food plaiit,i7, 117. 

Agassiz, L.. quoted, 133. 

Agraulii vanillae, 76. 

Androconia, lai. 

Angle-wings, 35, 165. 

Anosia plex]pi>us: see Milk- 
weed Butterfly. 

Anteniue, stnicCuK of, 114. 

Anthochirini, 144. 

Anthocharis genutia, 74. 

Antirrhea, 104. 

Apocynum a food plant, 17, 
48, 117. 

Apostiaphia chartthonia, 121;. 

AraUs aa food plant, 74. 

Argynnis atlanlia, 104. 

Aromatic butterflies, 104. 

Artificial flowers attracting 
butterflies, 128. 

Asclepias as food plant, 16, 

Asuuss, E. P., quoted, 69. 
Assembling of Lepidoptera, 

Atrophy of legs, 13, 134. 

Balance of Nature, jS. 
Bak, C., quoted, 144. 
Basilaichia, £3, 91 ; B. archip 

pus, 90, 93 { B. astyanax, 

Bates, H. W., quoted, 8a, 

B^kl*' in«c 

Blick Swallow-taif, 176. 

Bluss, 16. 

Bombycidae, assembling of. 

Broods, ginele and double, 

38, 167. 
Btush-footed butterHies, 138. 
BUCKX.KR, W., quoted, 70. 

early stajje ol , , , 
tile clothil^;, 1 60 ; in hiber- 
nation, 371 juvenile, i;c 

Chalcis, 76. 
Chlorippe clyton, 76. 
Chrysalis, d^gets of, 7;, 76 

suspension, 14a. 
Classification, 133. 
Clover as food plant, 127. 
Coenonympha pamphilus, 

Colors, vraming, 7j, 7^. 


caterpillars, 7; 

Coppers, 36. 

Cyanins pseudaigioius, 10; 
164, 169; C. p. luda, 170 
C. p. neglecta, 17OJ C. p 
[Hasus, 173; C. p. violacea 

17J; C. p. violacea-nigra 

Cycles of life, 3S, 



Danais arch^^pus, 151. 

Darwin, C, quoted, loi. 

Desiderata, 174. 

Dewitz, H., quoted, 18, 21. 

Didonis. 104. 

Dimorpnism, 162 ; double, 

164; seasonal, 167; sexual, 

Diosmism, to6. 
Distribution, geographical, 

Dorvphora clavicoUis, 80. 
Dusky-wings, ^y, 

Edwards, W. H., quoted, 

21, 3o» 33. 67, 70, I2S, 167. 

Egg, destruction of, 67; in 
nibemation, 35 ; of Milk- 
weed Butterfly, 13. 

Emigration of butterflies, 43. 

Ericaceae as food plants, 127. 

Euchaetes egle, 80. 

Euphoeades troilus, 93. 

Euploea, 150. 

Euploeinae, 83, 150, 179. 

Eurymus interior, 127; E. 
philodice, 127. 

Euvanessa antiopa, 35. 

Experiments, suggestions of, 
177; in vision, 113. 

Eyes of butterflies, structure 

of. III. 

Families of butterflies, 138, 

Favored butterflies, 82. 

Food plant of Milkweed But- 
terfly, 16; selected by 
smell, 130. 

Fore legs, structure of, 13, 


FoREL, A., quoted, iii. 

Fritillaries, 92. 

Genera, limitations of, 153. 
Glandular hairs, 160; scales, 

Gossamer-wings, 69, 138. 

Groups in butterflies, 178. 
GuLiCK, L. H., quoted, 53. 
GuNDLACH, J., quoted, 17, 

Haase, E., quoted, 123. 
Habits of caterpillar, 17. 
Hair-streaks, 36. 
Hamilton, J. quoted, 48. 
Hesperidae, 138, 139, 142. 
Hibernation, 35 ; of butter- 

%> 35 5 of caterpillar, 37; 

of chrysalis, 37; of egg, 

Howard, L. O., quoted, 76. 

Ichneumon-flies, 31, 71, 76. 

Imago: see Milkweed But- 
terfly Butterfly. 

Immigration in butterflies, 42. 

Infantile clothing of cater- 
pillars, 160. 

Insect vision, no. 

Instinct, 128. 

Involuti, 143. 

Iphiclides ajax, 167; I. a. 
ajax, 168 ; I. a. marcellus, 
168 ; I. a. telamonides, 168. 

Ithomyiae, Z^. 

Ithomyini, 179. 

Jasoniades glaucus, 164. 
juvenile caterpillars, 159. 

Larva : see Caterpillar. 
Legs, atrophy of, 13, 134; 
gradation in structure of, 

Leguminosae as food plants, 


Lemoniinae, 138, 141, 144. 

Leptalides, 83. 

Libytheinae, liii. 

Life history of Dutterflies, 30. 

Limnaini, 179. 

Lycaenidae, 138, 140, 143. 

Lycaenids, 36! 

Lycaeninae, 69, 138, 140. 





Malodorous butterflies, Si. 
Meadow-browns, 37. 
Melete, 105. 
Migration of butterflies, 42, 

Milkweed Butterfly, i ; broods, 
33; cycles, 33; desiderata, 
1 74 ; distribution, 40; found 
in Asia, 59 ; in Europe, 60; 
in high north, 47 ; in Pacific 
Islands, 54 ; life history, 30 ; 
parasites, 68, 71; protec- 
tion, 80; suggestions for 
experiments, 177. 

Milkweed Butterfly Butterfiy, 
12; atrophy of fore legs, 
13, 134; broods, 33; emi- 
gration, 43 ; fore legs, 13, 
134; hibernation, 30; im- 
migration, 43; legs, 13, 
134; life, 30; migration, 
43; mimicKed, 83, 90; 
odor, 81, 105; pouch in 
wing, 13; scales of male, 
97 ; seasons, 30; swarming, 
48; tongue, 23; vagrancy, 
40; variations require study, 
178; wanderings abroad, 
53; warning colors, 83; 
wing-pouch, 13. 

Milkweed Butterfly Caterpil- 
lar ^ 14, 31 ; conspicuous 
colors. 73; early stage, 15, 
159; food plant, 16; habits, 
17, 31; juvenile, 15, 159; 
moulting, 18 ; mouth-parts, 
26 ; warning colors, 73. 

Milkweed Butterfly Chrysa- 
lis^ 15 ; duration, 21 ; sus- 
pension, 32. 

Milkweed Butterfly £j^, 13; 
where laid, 16, 31. 

Mimicry, 70, 89. 

Mistakes of vision, 122. 

Moulting of caterpillar, 19. 

Mourning-cloak, 35. 

Mouth-parts, 23. 

MUller, F., quoted, 26, 102, 

Names, 148. 

Nauseous butterflies, 81. 

Nomenclature, its necessity, 

Nymphalidae, 138, 141, 144, 

145, 150. 
Nymphalis, 150. 

Odor of butterflies, 81, 104; 
of plants, 129. 

Papilio, 154; P. poIydamaSy 

106; P. polyxenes, 176. 
Papilionidae, 138, 143. 
Papilioninae, 138, 139. 
Papillae of tongue, 25. 
Parasites, 67^ 71, 76. 
Parastatic mimicry, 89. 
Pamassini, 144. 
Pamassius, 36. 
Patten, W., quoted, iit. 
Peale, T. R., quoted, 22. 
Penduli, 144. 
Pholisora, 37. 
Phylogeny of butterflies, 146, 

Physiological selection, 166. 
Pierinae, 138, 140. 
Pieris napi^ 106 ; P. oleracea, 

106, 178; P. rapae, 178. 
Plateau, F., quoted, iii, 

112, 113, 118. 
Polygonia interrogationis, 67, 

Poucn in wing, 13. 
Prittwitz, O. von, quoted, 

Protective resemblance, 79. 
Pteromalines, 76. 
Pupa : see Chiysalis. 

Reptiles as foes, 72. 
Riley, C. V., quoted, 16, 

Romanes, G. J., quoted, 

Satyrids, 37, 145, 
Scale patches, 163. 



Scales, 97. 

Scent in butterflies, 81, 129. 
Scent-scales, 96. 
ScHWARZ, C, quoted, 70. 
Seasonal dimorphism, 167. 
Secondary sexual characters, 


Secretory glands, 103, 160. 
Selection, sexual, 96, loi, 

Semnopsyche diana, 92. 

Semper, C, quoted, 56. 

Sexual characteristics, 13 ; di- 
morphism, 162; selection, 
96, loi, 131. 

Skippers, 100, 138. 

SmeU, its function in butter- 
flies, no. 

Sptring azure, 164, 169. 

Stichophthalma, 104. 

" Struggle for existence," 30, 
65. 82. 

Subdivisions of butterflies, 
138, 1^0. 

Succincti, 144. 

Suggestions for experiments, 

Suspensi, 144. 

Suspension of chrysalids, 143. 

Swallow-tails, j^i i<^0) >35* 

Swarming in butterflies, 47. 
Systematic zoology, 1 54. 

Tachinid flies, 71. 
Tasitia berenice, 83. 
Tetraopes tetraophthalmus, 

Thanaos, vj. 
Tiger Swallow-tail, 164. 
Tongue, 23. 
Tribes, 155. 
Typical Initterflies, 138. 

Vacdnium as food plant, 127. 
Variation in butterflies, 162. 
Violet-tip, 67. 
Vision, no ; mistakes of, 122. 

Walker, J. T., quoted, 57. 
Wallace, A. R., quoted, 


Wanderings of Milkweed 

Butterfly, 53. 
Warning colors, 73. 
Wasps, mistakes of vision in, 

Weismann, a., quoti^i^ua. 
Wings, origin 01, 156. 

Zebra Swallow-tail, 167.